Brake issue on 97 Blazer

I have been fighting the issue for about a year now. We were out on a drive one day, and we pulled off an exit ramp to turn onto another road. When we started moving after we turned, the thing wouldnt shift into 2nd. I stopped, tried it again, and it did the same thing. So, since i was close to a town, I turned around and headed that way. While heading towards town, I noticed the speedo wasnt working. So, I sped up a bit more to see what it would do. All of the sudden, I got to about 35 MPH's and the speedometer jumped up and it shifted into 2nd. Anyway, long story short, I replaced the VSS later that day, and it fixed the speedo problem and shifting problem just like I figured it would. Here's where it gets weird. A few days later, we started noticing that the brake pedal would drop like the master cylinder was going out, but then the ABS would kick in like it was loosing traction. I put my scan tool on, and it didnt find any ABS codes. What was weird though is it said the speed on all wheels was 5 mph at a dead stand still. So, I cleaned all the wheel sensors and put it together and drove it and it seemed fine. A couple of days later, it started doing it again. I scanned it again, and it came back negative again for codes, but it still says the wheel speed is 5 mph at a stand still. I unplugged the wire loom form the ABS controller and drove it. No problems at all, except of course that the light was on. I bought a used controller off Ebay, and it did the same thing. I am beginning to think that I need a new VSS, but why would the speedo work right if the VSS was screwed up? I am about out of ideas on this...

Do you have an abs capable scanner that looks at comparative individual wheel speeds?

Yes, I do. I have an OTC 4000E with the 98 ABS cartridge. It shows 5 MPH at the front wheels and the rear wheels. Whats weird though is that at about 17-19 MPH, it drops to 0 MPH on all wheels, and then jumps back up past that. When you slow back down to 17-19, it drops to 0 on front and back readings, then pops back up below that, but never drops below 5 MPH, except at 17-19 MPH.

DIAGNOSIS & TESTING
NOTE: When testing and diagnosing 4WAL system, use of Tech 2 scan
tool is required.
The Electronic Brake Control Module (EBCM) performs a selfdiagnosis
of the ABS system. The EBCM detects and isolated system
failures, then sets the corresponding diagnostic trouble code (DTC).
Before diagnosing 4WAL system, perform a comprehensive visual
inspection of system by checking wiring harness connectors, harness
routing (pay particular attention to wheel speed sensor wiring harness
routing), applicable fuses in fuse block, and ground connections.
Ensure brake fluid level in master cylinder reservoir is full.
Start 4WAL system diagnosis using DIAGNOSTIC SYSTEM CHECK. If
failures are found when performing diagnostic system check, you will
be directed to enter diagnostics to retrieve DTCs or perform SYMPTOM
TESTS. Diagnostic system check may indicate that system is functioning
properly.
RETRIEVING DTCS
Connect Tech 2 scan tool to DLC located under steering
column. Access 4WAL brake DTCs. Repair DTCs in the order they appear.
See 4WAL DIAGNOSTIC TROUBLE CODE (DTC) table for diagnosis. Before
diagnosing DTC(s), perform DIAGNOSTIC SYSTEM CHECK.
4WAL DIAGNOSTIC TROUBLE CODE (DTC)
C0221 .................. Right Front Wheel Speed Sensor Circuit Open
C0222 ................ Right Front Wheel Speed Sensor Signal Missing
C0223 ................ Right Front Wheel Speed Sensor Signal Erratic
C0225 ................... Left Front Wheel Speed Sensor Circuit Open
C0226 ................. Left Front Wheel Speed Sensor Signal Missing
C0227 ................. Left Front Wheel Speed Sensor Signal Erratic
C0229 ................................ Simultaneous Dropout Of Front
C0235 .................................... Wheel Speed Sensor Signal
C0236 ........................ Rear Speed Sensor Signal Circuit Open
C0237 ............................. Rear Speed Sensor Signal Missing
C0238 ............................. Rear Speed Sensor Signal Erratic
C0241-C0254 ................................... Wheel Speed Mismatch
C0265 or C0266 .......................... EBCM Control Valve Circuit
C0267 or C0268 ..................... Pump Motor Circuit Open/Shorted
C0269 or C0274 ....................... Excessive Dump/Isolation Time
C0271-C0273 .................................... EBCM Internal Fault
C0281 ......................................... Brake Switch Circuit
C0286 ....................... ABS Indicator Light Circuit Shorted To
Battery Voltage
C0288 ....................... Brake Warning Light Circuit Shorted To
Battery Voltage EBCM Relay Circuit
(1) - Always perform DIAGNOSTIC SYSTEM CHECK before performing DTC
tests.
DIAGNOSTIC SYSTEM CHECK
NOTE: For circuit reference, see WIRING DIAGRAMS.
System Description
The diagnostic system check is an organized approach to
identifying a problem created by an ABS malfunction. It must be the
starting point of any ABS complaint diagnosis because it directs to
the next logical step in diagnosing the complaint.
Serial data is exchanged by EBCM through harness connector
C1, terminal "F", and Class 2 data is exchanged through harness
connector C1, terminal "G". EBCM is supplied switched ignition voltage
through harness connector C1, terminal "A", and ground is provided
through harness connector C1, terminal "J".
Diagnosis
1) Verify all EBCM connectors are connected properly. Install
scan tool. Turn ignition switch to RUN position. Using scan tool, try
to communicate with the EBCM. If data is being received from EBCM, go
to next step. If data is not received from EBCM, go to step 4).
2) Using the scan tool, record any current or history DTCs.
If any DTCs are present, see 4WAL DIAGNOSTIC TROUBLE CODE (DTC) table.
If DTC(s) are not present, go to next step.
3) Turn ignition off for 10 seconds. Turn ignition switch to
RUN position and observe the ABS indicator lamp. If the lamp is on for
3 seconds then goes out, the system is operating normally. If not, go
to step 11).
4) Turn ignition off. Disconnect the 10-way EBCM harness
connector. Turn ignition switch to RUN position. Measure voltage between EBCM harness connector terminal A and ground. If the voltage
is between 10-15 volts, go to next step. If not, go to step 9).
5) Disconnect negative battery terminal. Disconnect 10-pin
EBCM harness connector. Check resistance between negative battery
terminal and 10-pin EBCM harness connector terminal "J". If resistance
is 0-2 ohms, go to step 6). If resistance is not 0-2 ohms, go to step
12).
6) Inspect EBCM and EBCM harness connector terminals for poor
contact. Inspect battery terminals and battery cable terminals for
poor connection. Repair as necessary. Is there a poor connection, then
go to step 7). If connections or terminals are okay, go to step 8).
7) Repair the poor connection. After repairs, go to step 1).
8) Reconnect EBCM harness connectors and battery terminals.
If communications cannot be established between scan tool and EBCM,
try scan tool on similar vehicle with the same system to determine if
scan too is malfunctioning or if Class 2 data line is faulty. See
appropriate diagram in DATA LINK CONNECTORS article in WIRING
DIAGRAMS. Repair or replace as necessary.
9) Disconnect positive battery cable. Turn ignition switch to
RUN position. Measure resistance between the positive battery cable
and terminal A of the EBCM. If the resistance is 0-2 ohms, go to next
step. If not, go to step 13).
10) Turn ignition off. Remove 10 amp ABS/Brake fuse. Measure
resistance between EBCM terminal "A" and ground. If the resistance is
infinite, go to step 15). If not, go to step 14).
11) Observe the ABS light. If ABS light stays on, go to step
18). If not, go to step 21).
12) Repair open or high resistance in circuit No. 451. After
repairs, repeat step 1).
13) Repair open or high resistance in circuit No. 441. Check
10 amp ABS/Brake fuse. After repairs, repeat step 1).
14) Repair short to ground in circuit No. 441. Check circuit
breaker. After repairs, repeat step 1).
15) Inspect ignition and brake switch input circuits and 10-
pin EBCM harness connector C1 for physical damage, which could cause a
short to ground with EBCM harness connector connected to EBCM. Repair
as necessary. If damage is found, go to step 16). If no damage is
found, go to step 17).
16) Repair damaged terminals. After repairs, go to step 1).
17) Check 10-amp ABS/Brake fuse. If the fuse is good, replace
the EBCM. After repairs, repeat step 1).
18) Use scan tool to turn off the ABS light. If the light
goes off, go to next step. If not, go to step 20).
19) Replace the instrument cluster. After repairs, repeat
step 1).
20) Replace EBCM. After repairs, repeat step 1).
SYMPTOM TESTS
NOTE: To identify the circuits and wire colors referenced in
testing, see WIRING DIAGRAMS. After repairs, recheck system
operation to verify problem has been repaired. See DIAGNOSTIC
SYSTEM CHECK under DIAGNOSIS & TESTING.
TEST A: ANTI-LOCK LIGHT DOES NOT ILLUMINATE - NO DTCS
Circuit Description
The EBCM controls the ANTI-LOCK indicator light by supplying
ground to turn on or battery voltage to turn off the indicator light.
If indicator light is off constantly, check for an open or
short to voltage in the light circuit between indicator light and
EBCM. Also check for open in GAUGES fuse or faulty light bulb.
16) Repair damaged terminals. After repairs, go to step 1).
17) Check 10-amp ABS/Brake fuse. If the fuse is good, replace
the EBCM. After repairs, repeat step 1).
18) Use scan tool to turn off the ABS light. If the light
goes off, go to next step. If not, go to step 20).
19) Replace the instrument cluster. After repairs, repeat
step 1).
20) Replace EBCM. After repairs, repeat step 1).
SYMPTOM TESTS
NOTE: To identify the circuits and wire colors referenced in
testing, see WIRING DIAGRAMS. After repairs, recheck system
operation to verify problem has been repaired. See DIAGNOSTIC
SYSTEM CHECK under DIAGNOSIS & TESTING.
TEST A: ANTI-LOCK LIGHT DOES NOT ILLUMINATE - NO DTCS
Circuit Description
The EBCM controls the ANTI-LOCK indicator light by supplying
ground to turn on or battery voltage to turn off the indicator light.
If indicator light is off constantly, check for an open or
short to voltage in the light circuit between indicator light and
EBCM. Also check for open in GAUGES fuse or faulty light bulb.
TEST B: ANTI-LOCK LIGHT IS ON AT ALL TIMES - NO DTCS
Circuit Description
The EBCM controls the ANTI-LOCK indicator light by supplying
ground to turn on or battery voltage to turn off the indicator light.
If indicator light is on constantly, check for short to
ground in the light circuit between indicator light and EBCM, or EBCM
is not capable of turning off indicator light.
Diagnosis
1) Perform Diagnostic System Check. If diagnostic system
check has been performed, go to next step. If not, go to DIAGNOSTIC
SYSTEM CHECK.
2) Turn ignition off. Disconnect 10-pin EBCM harness
connector from EBCM. Turn ignition switch to RUN position. If ANTILOCK
indicator light illuminates and stays illuminated, go to step 4).
If not, go to next step.
3) Replace EBCM.
4) Repair short to ground in ANTI-LOCK indicator light
control circuit between instrument cluster and EBCM.
DIAGNOSTIC TESTS
NOTE: To identify the circuits and wire colors referenced
in testing, see WIRING DIAGRAMS. After repairs, recheck
system operation to verify problem has been repaired. See
DIAGNOSTIC SYSTEM CHECK under DIAGNOSIS & TESTING.
WSS TEMPERATURE-VS-SENSOR RESISTANCE
DTC C0221: RIGHT FRONT WHEEL SPEED SENSOR CIRCUIT OPEN
Circuit Description
As a toothed ring passes by the Wheel Speed Sensor (WSS),
changes in electromagnetic field cause wheel speed sensor to produce
an AC voltage signal. Voltage signal frequency and amplitude are
proportional to wheel speed. The magnitude of this signal is directly
related to wheel speed and proximity of wheel speed sensor to toothed
ring, often referred to as the air gap.
Conditions for setting DTC:
* No output signal from right front wheel sensor for one
second.
* Excessive right front wheel speed sensor resistance for one
second.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 4-pin EBCM harness
connector. Check resistance between 4-pin harness connector terminals
"C" and "E". See WSS TEMPERATURE-VS-SENSOR RESISTANCE table. If
resistance is as specified, go to step 5). If not, go to next step.
3) Disconnect right WSS harness connector. Using a fused
jumper wire, jumper sensor harness connector terminals "A" and "B".
Using DVOM, check resistance between 4-pin EBCM harness connector
terminals "C" and "E". If resistance is 0-2 ohms, go to next step. If
not, go to step 10).
4) Check resistance between right WSS harness connector
terminals "A" and "B". See WSS TEMPERATURE-VS-SENSOR RESISTANCE table.
If resistance is as specified, go to step 7). If not, go to step 11).
5) Inspect 4-pin EBCM harness connector for signs of damage
or corrosion. If damage is present, go to step 8). If no signs of
damage are present, go to next step.
6) Reconnect all harness connectors. Test drive vehicle at
speed greater than 15 MPH. If DTC C0221 sets, go to step 9). If not,
go to next step.
7) Malfunction is intermittent. Check all connectors and
harnesses for damage which may result in high resistance when
components are connected. See DIAGNOSTIC AIDS.
8) Repair 4-pin EBCM harness connector.
9) Replace EBCM.
10) Repair open or high resistance in wheel speed sensor
circuits between sensor and EBCM.
11) Replace wheel speed sensor.
Diagnostic Aids
An intermittent malfunction may be caused by a poor
connection, rubbed-through wire insulation, or a wire broken inside
the insulation. Also, check sensor terminals harness connectors.
DTC C0222: RIGHT FRONT WHEEL SPEED SENSOR SIGNAL MISSING
Circuit Description
As a toothed ring passes by the Wheel Speed Sensor (WSS),
changes in the electromagnetic field cause the wheel speed sensor to
produce an AC voltage signal. Voltage signal frequency and amplitude
are proportional to wheel speed. The magnitude of this signal is
directly related to wheel speed and proximity of wheel speed sensor to
toothed ring, often referred to as the air gap.
Conditions for setting DTC:
* Right front wheel speed is less than 4 MPH.
* All other wheel speeds are greater than 8 MPH.
* Unexpected wheel acceleration/deceleration. Anything that
keeps the right front wheel speed sensor signal low while
vehicle is moving at greater than 8 MPH.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Inspect right front wheel speed sensor,
sensor cable and connectors for signs of damage or corrosion. Inspect
wheel sensor toothed ring for looseness. Inspect 4-pin EBCM harness
connector. If any damage is found, go to step 7). If no damage is
found, go to next step.
3) Raise and support vehicle. Disconnect right front WSS
harness connector. Using DVOM, check resistance between sensor
terminals "A" and "B". See WSS TEMPERATURE-VS-SENSOR RESISTANCE table.
If resistance is as specified, go to next step. If not, go to step 8).
4) Select AC scale on DVOM. Connect DVOM to sensor terminals
"A" and "B". Spin wheel by hand while observing voltage reading on
DVOM. If DVOM reads greater than 100 mV, go to next step. If not, go
to step 8).
5) Disconnect 4-pin EBCM harness connector. Check resistance
between harness connector terminals "C" and "E". If reading is
infinite, go to next step. If reading is not infinite, go to step 10).
6) Reconnect all harness connectors. Test drive vehicle at
speed greater than 15 MPH. If DTC C0222 sets, go to step 9). If not,
go to step 11).
7) Make necessary repairs.
8) Replace right front wheel speed sensor.
9) Replace EBCM.
10) Repair short between wheel speed sensor circuits.
11) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
Diagnostic Aids
An intermittent malfunction may be caused by a poor
connection, rubbed-through wire insulation, or a wire broken inside
the insulation. Also, check sensor terminals harness connectors.
DTC C0223: RIGHT FRONT WHEEL SPEED SENSOR SIGNAL ERRATIC
Circuit Description
As a toothed ring passes by the Wheel Speed Sensor (WSS),
changes in the electromagnetic field cause the wheel speed sensor to
produce an AC voltage signal. Voltage signal frequency and amplitude
are proportional to wheel speed. The magnitude of this signal is
directly related to wheel speed and proximity of wheel speed sensor to
toothed ring, often referred to as the air gap.
Conditions for setting DTC:
* Average wheel speed for all wheel speed signals is greater
than 25 MPH.
* Average right front wheel speed is greater than 25 MPH.
* No output from right front wheel speed signal for 15
milliseconds. Anything which suddenly prevents (intermittent)
the right front wheel speed signal to drop to zero while
vehicle is moving greater than 25 MPH.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 4-pin EBCM harness connector
and inspect for signs of corrosion or damage. Inspect wheel speed
sensor, sensor cable and connectors for signs of damage or corrosion.
If connections are okay, go to next step. If connections are damaged
or corroded, go to step 6).
3) Using DVOM, check resistance between 4-pin EBCM harness
connector terminals "C" and "E". Wiggle harness in various locations
while monitoring DVOM reading. See WSS TEMPERATURE-VS-SENSOR
RESISTANCE table. If resistance is as specified and does not
fluctuate, go to step 5). If not, go to next step.
4) Disconnect wheel speed sensor harness connector. Check
resistance between wheel sensor terminals "A" and "B". See WSS
TEMPERATURE-VS-SENSOR RESISTANCE table. If resistance is as specified,
go to step 7). If not, go to step 8).
5) Reconnect all harness connectors. Remove right front tire,
hub and rotor. Verify right front wheel speed sensor is securely
mounted and tone wheel is in good condition. If damage is not found,
go to step 9). If damage is found, go to step 10).
6) Make necessary repairs.
7) Repair open, short or high resistance in wheel speed
sensor circuits.
8) Replace wheel speed sensor. After replacing sensor,
perform DIAGNOSTIC SYSTEM CHECK.
9) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
10) Make necessary repairs.
Diagnostic Aids
An intermittent malfunction may be caused by a poor
connection, rubbed-through wire insulation, or a wire broken inside
the insulation. Also, check sensor terminals harness connectors.
DTC C0225: LEFT FRONT WHEEL SPEED SENSOR CIRCUIT OPEN
Circuit Description
As a toothed ring passes by the Wheel Speed Sensor (WSS),
changes in the electromagnetic field cause the wheel speed sensor to
produce an AC voltage signal. Voltage signal frequency and amplitude
are proportional to wheel speed. The magnitude of this signal is
directly related to wheel speed and proximity of wheel speed sensor to
toothed ring, often referred to as the air gap.
Conditions for setting DTC:
* No output signal from left front wheel sensor for one
second.
* Excessive left front wheel speed sensor resistance for one
second.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 4-pin EBCM harness
connector. Check resistance between 4-pin harness connector terminals
"A" and "D". See WSS TEMPERATURE-VS-SENSOR RESISTANCE table. If
resistance is as specified, go to step 5). If not, go to next step.
3) Disconnect left WSS harness connector. Using a fused
jumper wire, jumper sensor harness connector terminals "A" and "B".
Using DVOM, check resistance between 4-pin EBCM harness connector
terminals "A" and "D". If sensor resistance is 0-2 ohms, go to next
step. If not, go to step 10).
4) Check resistance between right WSS harness connector
terminals "A" and "B". See WSS TEMPERATURE-VS-SENSOR RESISTANCE table.
If resistance is as specified, go to step 7). If not, go to step 11).
5) Inspect 4-pin EBCM harness connector for signs of damage
or corrosion. If damage is present, go to step 8). If no signs of
damage are present, go to next step.
6) Reconnect all harness connectors. Test drive vehicle at
speed greater than 15 MPH. If DTC C0225 sets, go to step 9). If not,
go to next step.
7) Malfunction is intermittent. Check all connectors and
harnesses for damage which may result in high resistance when
components are connected. See DIAGNOSTIC AIDS.
8) Repair 4-pin EBCM harness connector.
9) Replace EBCM.
10) Repair open or high resistance in wheel speed sensor
circuits.
11) Replace wheel speed sensor. After replacing sensor,
perform DIAGNOSTIC SYSTEM CHECK.
Diagnostic Aids
An intermittent malfunction may be caused by a poor
connection, rubbed-through wire insulation, or a wire broken inside
the insulation. Also, check sensor terminals harness connectors.
DTC C0226: LEFT FRONT WHEEL SPEED SENSOR SIGNAL MISSING
Circuit Description
As a toothed ring passes by the Wheel Speed Sensor (WSS),
changes in the electromagnetic field cause the wheel speed sensor to
produce an AC voltage signal. Voltage signal frequency and amplitude
are proportional to wheel speed. The magnitude of this signal is
directly related to wheel speed and proximity of wheel speed sensor to
toothed ring, often referred to as the air gap.Conditions for setting DTC:
* Left front wheel speed is less than 4 MPH.
* All other wheel speeds are greater than 8 MPH.
* No unexpected wheel acceleration/deceleration. Anything that
keeps the left front wheel speed sensor signal low while
vehicle is moving at greater than 8 MPH.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Inspect left front wheel speed sensor,
sensor cable and connectors for signs of damage or corrosion. Inspect
wheel sensor toothed ring for looseness. Inspect 4-pin EBCM harness
connector. If any damage is found, go to step 7). If no damage is
found, go to next step.
3) Raise and support vehicle. Disconnect left front WSS
harness connector. Using DVOM, check resistance between sensor
terminals "A" and "B". See WSS TEMPERATURE-VS-SENSOR RESISTANCE table.
If resistance is as specified, go to next step. If not, go to step 8).
4) Select AC scale on DVOM. Connect DVOM to sensor terminals
"A" and "B". Spin wheel by hand while observing voltage reading on
DVOM. If DVOM reads greater than 100 mV, go to next step. If not, go
to step 8).
5) Disconnect 4-pin EBCM harness connector. Check resistance
between harness connector terminals "A" and "D". If reading is
infinite, go to next step. If reading is not infinite, go to step 10).
6) Reconnect all harness connectors. Test drive vehicle at
speed greater than 15 MPH. If DTC C0226 sets, go to step 9). If not,
go to step 11).
7) Make necessary repairs.
8) Replace left front wheel speed sensor. After replacing
sensor, perform DIAGNOSTIC SYSTEM CHECK.
9) Replace EBCM.
10) Repair short between wheel speed sensor circuits.
11) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
Diagnostic Aids
An intermittent malfunction may be caused by a poor
connection, rubbed-through wire insulation, or a wire broken inside
the insulation. Also, check sensor terminals harness connectors.
DTC C0227: LEFT FRONT WHEEL SPEED SENSOR SIGNAL ERRATIC
Circuit Description
As a toothed ring passes by the Wheel Speed Sensor (WSS),
changes in the electromagnetic field cause the wheel speed sensor to
produce an AC voltage signal. Voltage signal frequency and amplitude
are proportional to wheel speed. The magnitude of this signal is
directly related to wheel speed and proximity of wheel speed sensor to
toothed ring, often referred to as the air gap.
Conditions for setting DTC:
* Average wheel speed for all wheel speed signals is greater
than 25 MPH.
* Average left front wheel speed is greater than 25 MPH.
* No output from left front wheel speed signal for 15
milliseconds. Anything which suddenly prevents (intermittent)
the right front wheel speed signal to drop to zero while
vehicle is moving greater than 25 MPH.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 4-pin EBCM harness connector
and inspect for signs of corrosion or damage. Inspect wheel speed
sensor, sensor cable and connectors for signs of damage or corrosion.
If connections are okay, go to next step. If connections are damaged
or corroded, go to step 6).
3) Using DVOM, check resistance between 4-pin EBCM harness
connector terminals "A" and "D". Wiggle harness in various locations
while monitoring DVOM reading. See WSS TEMPERATURE-VS-SENSOR
RESISTANCE table. If resistance is as specified and does not
fluctuate, go to step 5). If not, go to next step.
4) Disconnect wheel speed sensor harness connector. Check
resistance between wheel sensor terminals "A" and "B". See WSS
TEMPERATURE-VS-SENSOR RESISTANCE table. If resistance is as specified,
go to step 7). If not, go to step 8).
5) Reconnect all harness connectors. Remove left front tire,
hub and rotor. Verify right front wheel speed sensor is securely
mounted and tone wheel is in good condition. If damage is not found,
go to step 9). If damage is found, go to step 10).
6) Make necessary repairs.
7) Repair open, short or high resistance between wheel speed
sensor circuits.
8) Replace wheel speed sensor.
9) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
10) Make necessary repairs.
Diagnostic Aids
An intermittent malfunction may be caused by a poor
connection, rubbed-through wire insulation, or a wire broken inside
the insulation. Also, check sensor terminals harness connectors.
DTC C0229: DROP OUT OF FRONT WHEEL SPEED SENSOR SIGNALS
Circuit Description
As a toothed ring passes by the Wheel Speed Sensor (WSS),
changes in the electromagnetic field cause the wheel speed sensor to
produce an AC voltage signal. Voltage signal frequency and amplitude
are proportional to wheel speed. The magnitude of this signal is
directly related to wheel speed and proximity of wheel speed sensor to
toothed ring, often referred to as the air gap.
Conditions for setting DTC:
* EBCM losing both front wheel speed signals when vehicle is at
speeds greater than 12 MPH (brake released) or 20 MPH (brake
applied).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 4-pin EBCM harness
connector. Inspect harness connector and terminals for damage or
corrosion. If harness or terminal is damaged or corroded, go to step
4). If harness and terminal are okay, go to next step.
3) Reconnect harness connector. Clear DTC. Road test vehicle
at speeds greater than 15 MPH. Retrieve DTCs. If DTC C0229 resets, go
to step 5). If DTC does not reset, go to step 6).
4) Make necessary repairs to harness connector or terminals.
5) Replace EBCM.
6) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
Diagnostic Aids
An intermittent malfunction may be caused by a poor
connection, rubbed-through wire insulation, or a wire broken inside
the insulation. Also, check sensor terminals harness connectors.
DTC C0235: REAR SPEED SENSOR SIGNAL CIRCUIT OPEN OR
GROUNDED (GASOLINE ENGINES)
Circuit Description
The rear wheel speed sensor signal originates from the VSS
which is connected to the PCM/VCM. The EBCM receives the rear wheel
speed sensor signal from the PCM/VCM.
Conditions for setting DTC:
* EBCM not seeing the correct voltage level from the PCM/VCM at
start-up.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 10-pin EBCM harness
connector. Turn ignition switch to RUN position. Check voltage between
10-pin EBCM harness connector terminal "E" and ground. If voltage is
greater than 10 volts, go to step 4). If not, go to next step.
3) Turn ignition off. Disconnect PCM/VCM harness connector
C1. Check resistance between 10-pin EBCM harness connector terminal
"E" and PCM/VCM harness connector terminal No. 15 (terminal No. 70 on
2.2L engines). If resistance is 0-2 ohms, go to step 5). If not, go to
step 8).
4) Turn ignition off. Reconnect PCM/VCM harness connector.
Turn ignition switch to RUN position. Using scan tool, clear DTCs.
Test drive vehicle at speed greater than 15 MPH. Check for DTCs. If
DTC C0235 resets, go to step 6). If DTC does not reset, go to step 7).
5) Check resistance between 10-pin EBCM harness connector
terminal "E" and ground. If resistance is infinite, check VSS. If
resistance is not infinite, go to step 9).
6) Replace EBCM.
7) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
8) Repair open in VSS signal circuit between VCM and EBCM.
9) Repair short to ground in VSS signal circuit.
Diagnostic Aids
This DTC can be set by a faulty VSS or a fault in VSS signal
circuit.
DTC C0235: REAR SPEED SENSOR SIGNAL CIRCUIT OPEN OR
GROUNDED (DIESEL ENGINES)
Circuit Description
The rear wheel speed sensor signal originates from the VSS
buffer. The EBCM receives the rear wheel speed sensor signal from the
VSS buffer
Conditions for setting DTC:
* EBCM not seeing correct voltage level from PCM at start-up.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 10-pin EBCM harness
connector. Turn ignition switch to RUN position. Check voltage between
10-pin EBCM harness connector terminal "E" and ground. If voltage is
greater than 10 volts, go to step 4). If not, go to next step.
3) Turn ignition off. Disconnect VCM harness connector. Check
resistance between 10-pin EBCM harness connector terminal "E" and VCM
harness connector terminal No. 10 (VSS signal output). If resistance
is infinite, go to step 5). If not, go to step 8).
4) Turn ignition off. Reconnect VCM harness connector. Turn
ignition switch to RUN position. Using scan tool, clear DTCs. Test
drive vehicle at speed greater than 15 MPH. Check for DTCs. If DTC
C0235 resets, go to step 6). If DTC does not reset, go to step 7).
5) Check resistance between 10-pin EBCM harness connector
terminal "E" and ground. If resistance is infinite, check VSS. If
resistance is not infinite, go to step 9).
6) Replace EBCM.
7) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
8) Repair open in VSS signal circuit between EBCM and VCM.
9) Repair short to ground in VSS signal circuit.
Diagnostic Aids
A fault in VSS signal circuit can cause this DTC to set. If
voltage readings are low or varying, the battery, charging system, or
intermittent connections could be the cause. Check these areas before
replacing any components.
DTC C0236: REAR SPEED SENSOR SIGNAL MISSING (GASOLINE
ENGINES)
Circuit Description
The rear wheel speed sensor signal originates from the VSS
which is connected to the PCM/VCM. The EBCM receives the rear wheel
speed sensor signal from the PCM/VCM.
Conditions for setting DTC:
* EBCM losing rear wheel speed signal for at least 5 seconds at
speeds greater than 8 MPH with brake pedal released. If DTC
C0235 is also present, diagnose that DTC first.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 10-pin EBCM harness
connector. Turn ignition switch to RUN position. Check voltage between
10-pin EBCM harness connector terminal "E" and ground. If voltage is
greater than 10 volts, go to step 4). If not, go to next step.
3) Turn ignition off. Disconnect PCM/VCM harness connector
C1. Check resistance between 10-pin EBCM harness connector terminal
"E" and PCM/VCM harness connector terminal No. 15 (terminal No. 70 on
2.2L engines). If resistance is 0-2 ohms, go to step 5). If not, go to
step 8).
4) Turn ignition off. Reconnect PCM/VCM harness connector.
Turn ignition switch to RUN position. Using scan tool, clear DTCs.
Test drive vehicle at speed greater than 15 MPH. Check for DTCs. If
DTC C0236 resets, go to step 6). If DTC does not reset, go to step 7).
5) Check resistance between 10-pin EBCM harness connector
terminal "E" and ground. If resistance is infinite, check VSS. If
resistance is not infinite, go to step 9).
6) Replace EBCM.
7) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
8) Repair open in VSS signal circuit between VCM and EBCM.
9) Repair short to ground in VSS signal circuit.
Diagnostic Aids
This DTC can be set by a faulty VSS or a fault in VSS signal
circuit between EBCM and VCM.
DTC C0236: REAR SPEED SENSOR SIGNAL MISSING (DIESEL ENGINES)
Circuit Description
The rear wheel speed sensor signal originates from the VSS
which is connected to the VSS buffer. The EBCM receives the rear wheel
speed sensor signal from the VSS buffer.
Conditions for setting DTC:
* EBCM losing rear wheel speed signal for at least 5 seconds at
speeds greater than 8 MPH with brake pedal released. If DTC
C0235 is also present, diagnose that DTC first.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 10-pin EBCM harness
connector. Turn ignition switch to RUN position. Check voltage between
10-pin EBCM harness connector terminal "E" and ground. If voltage is
greater than 10 volts, go to step 4). If not, go to next step.
3) Turn ignition off. Disconnect VCM harness connector C1.
Check resistance between 10-pin EBCM harness connector terminal "E"
and VCM harness connector terminal No. 15 (VSS signal output circuit).
If resistance is infinite, go to step 5). If not, go to step 8).
4) Turn ignition off. Reconnect VCM harness connector. Turn
ignition switch to RUN position. Using scan tool, clear DTCs. Test
drive vehicle at speed greater than 15 MPH. Check for DTCs. If DTC
C0236 resets, go to step 6). If DTC does not reset, go to step 7).
5) Check resistance between 10-pin EBCM harness connector
terminal "E" and ground. If resistance is infinite, check VSS. If
resistance is not infinite, go to step 9).
6) Replace EBCM.
7) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
8) Repair open in VSS signal circuit between EBCM and VCM.
9) Repair short to ground in VSS signal circuit.
Diagnostic Aids
This DTC can be set by a faulty VSS or a fault in VSS signal
circuits between EBCM and VCM.
DTC C0237: REAR SPEED SENSOR SIGNAL ERRATIC (GASOLINE
ENGINES)
Circuit Description
The rear wheel speed sensor signal originates from the VSS
which is connected to the VCM. The EBCM receives the rear wheel speed
sensor signal from the VCM.
Conditions for setting DTC:
* EBCM seeing the rear speed signal line drop out and return.
This DTC can be caused by a malfunction in the VSS or a fault
in VSS signal circuit.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 10-pin EBCM harness
connector. Turn ignition switch to RUN position. Check voltage between
10-pin EBCM harness connector terminal "E" and ground. If voltage is
greater than 10 volts, go to step 4). If not, go to next step.
3) Turn ignition off. Disconnect VCM harness connector C1.
Check resistance between 10-pin EBCM harness connector terminal "E"
and VCM harness connector terminal No. 15 (VSS signal output circuit).
If resistance is 0-2 ohms, go to step 5). If not, go to step 8).
4) Turn ignition off. Reconnect VCM harness connector. Turn
ignition switch to RUN position. Using scan tool, clear DTCs. Test
drive vehicle at speed greater than 15 MPH. Check for DTCs. If DTC
C0237 resets, go to step 6). If DTC does not reset, go to step 7).
5) Check resistance between 10-pin EBCM harness connector
terminal "E" and ground. If resistance is infinite, check VSS. If
resistance is not infinite, go to step 9).
6) Replace EBCM.
7) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
8) Repair open in VSS signal circuit between EBCM and VCM.
9) Repair short to ground in VSS signal circuit.
Diagnostic Aids
This DTC can be set by a faulty VSS or a fault in VSS signal
circuit between EBCM and VCM.
DTC C0237: REAR SPEED SENSOR SIGNAL ERRATIC (DIESEL ENGINES)
Circuit Description
The rear wheel speed sensor signal originates from the VSS
buffer. The EBCM receives the rear wheel speed sensor signal from the
VSS buffer.
Conditions for setting DTC:
* EBCM seeing the rear speed signal line drop out and return.
This DTC can be caused by a malfunction in the VSS or a fault
in VSS signal circuit.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 10-pin EBCM harness
connector. Turn ignition switch to RUN position. Check voltage between
10-pin EBCM harness connector terminal "E" and ground. If voltage is
greater than 10 volts, go to step 4). If not, go to next step.
3) Turn ignition off. Disconnect VCM harness connector C1.
Check resistance between 10-pin EBCM harness connector terminal "E"
and VCM harness connector terminal No. 15 (VSS signal output circuit).
If resistance is infinite, go to step 5). If not, go to step 8).
4) Turn ignition off. Reconnect all harness connectors. Turn
ignition switch to RUN position. Using scan tool, clear DTCs. Test
drive vehicle at speed greater than 15 MPH. Check for DTCs. If DTC
C0237 resets, go to step 6). If DTC does not reset, go to step 7).
5) Check resistance between 10-pin EBCM harness connector
terminal "E" and ground. If resistance is infinite, check VSS. If
resistance is not infinite, go to step 9).
6) Replace EBCM.
7) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when all
components are connected. See DIAGNOSTIC AIDS.
8) Repair open in VSS signal circuit between EBCM and VCM.
9) Repair short to ground in VSS signal circuit.
Diagnostic Aids
This DTC can be set by a faulty VSS or a fault in VSS signal
circuit between EBCM and VCM.
DTC C0238: WHEEL SPEED SIGNAL MALFUNCTION
Circuit Description
As a toothed ring passes by the Wheel Speed Sensor (WSS),
changes in the electromagnetic field cause the wheel speed sensor to
produce an AC voltage signal. Voltage signal frequency and amplitude
are proportional to wheel speed. The magnitude of this signal is
directly related to wheel speed and proximity of wheel speed sensor to
toothed ring, often referred to as the air gap.
Conditions for setting DTC:
* Any wheel speed differing from the vehicle speed for any of
the following causes:
* One mismatched wheel speed more than double or less than half
the other 3 wheel speeds.
* All 4 wheel speeds differing from each other by 8 percent.
* Vehicle speed greater than 12 MPH.
* No unexpected wheel acceleration. Anything that generates
consistent differences between wheel speed signals.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Inspect vehicle tires for variation in tire size. If all 4
tires are the same, go to next step.
3) Clear DTCs using scan tool. Test drive vehicle. While test
driving vehicle, use DATA LIST function on scan tool to monitor wheel
speeds. If scan tool indicates a faulty sensor, go to affected DTC
test to diagnose problem. If scan tool does not indicate a faulty
sensor, problem is intermittent.
DTC C0241: RIGHT FRONT ISOLATION SOLENOID CIRCUIT OPEN
Circuit Description
When right front isolation solenoid is needed, EBCM will
ground solenoid circuit to energize coil within solenoid. This will
close isolation valve by magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* Low voltage on EBCM solenoid driver circuit when expected to
be high (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could cause
loss of power to EBCM. If connector is okay, go to next step. If
connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fusible link. If fusible link is open, go to
step 9). If fusible link is okay, go to step 10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit.
DTC C0242: RIGHT FRONT DUMP SOLENOID CIRCUIT OPEN
Circuit Description
When right front dump solenoid is needed, EBCM will ground
solenoid circuit to energize coil within solenoid. This will open dump
valve by magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* Low voltage on EBCM solenoid driver circuit when expected to
be high (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fusible link. If fusible link is open, go to
step 9). If fusible link is okay, go to step 10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit.
DTC C0243: RIGHT FRONT ISOLATION SOLENOID CIRCUIT SHORTED
Circuit Description
When right front isolation solenoid is needed, EBCM will
ground solenoid circuit to energize coil within solenoid. This will
close isolation valve by magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* Low voltage on EBCM solenoid driver circuit when expected to
be high (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0244: RIGHT FRONT DUMP SOLENOID CIRCUIT SHORTED
Circuit Description
When right front dump solenoid is needed, EBCM will ground
solenoid circuit to energize coil within solenoid. This will open dump
valve by magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* Low voltage on EBCM solenoid driver circuit when expected to
be high (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0245: LEFT FRONT ISOLATION SOLENOID CIRCUIT OPEN
Circuit Description
When left front isolation solenoid is needed, EBCM will
ground solenoid circuit to energize coil within solenoid. This will
close isolation valve by magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* Low voltage on EBCM solenoid driver circuit when expected to
be high (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0246: LEFT FRONT DUMP SOLENOID CIRCUIT OPEN
Circuit Description
When left front dump solenoid is needed, EBCM will ground
solenoid circuit to energize coil within solenoid. This will open dump
valve by magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* Low voltage on EBCM solenoid driver circuit when expected to
be high (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0247: LEFT FRONT ISOLATION SOLENOID CIRCUIT SHORTED
Circuit Description
When left front isolation solenoid is needed, EBCM will
ground solenoid circuit to energize coil within solenoid. This will
close isolation valve by magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* High voltage on EBCM solenoid driver circuit when expected to
be low (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0248: LEFT FRONT DUMP SOLENOID CIRCUIT SHORTED
Circuit Description
When left front dump solenoid is needed, EBCM will ground
solenoid circuit to energize coil within solenoid. This will open dump
valve by magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* High voltage on EBCM solenoid driver circuit when expected to
be low (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0251: REAR ISOLATION SOLENOID CIRCUIT SHORTED
Circuit Description
When rear isolation solenoid is needed, EBCM will ground
solenoid circuit to energize coil within solenoid. This will close
isolation valve by magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* Low voltage on EBCM solenoid driver circuit when expected to
be high (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which can result
in loss of power to EBCM. If connector is okay, go to next step. If
connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0252: REAR DUMP SOLENOID CIRCUIT OPEN
Circuit Description
When rear dump solenoid is needed, EBCM will ground solenoid
circuit to energize coil within solenoid. This will open dump valve by
magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* Low voltage on EBCM solenoid driver circuit when expected to
be high (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0253: REAR ISOLATION SOLENOID CIRCUIT SHORTED
(EXCEPT "L" & "M" SERIES)
Circuit Description
When rear isolation solenoid is needed, EBCM will ground
solenoid circuit to energize coil within solenoid. This will open
isolation valve by magnetic force created by solenoid coil.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* Low voltage on EBCM solenoid driver circuit when expected to
be high (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse is open, go to
step 9). If fuse is okay, go to step 10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0254: REAR DUMP SOLENOID CIRCUIT SHORTED
Circuit Description
When rear dump solenoid is needed, EBCM will ground solenoid
circuit to energize coil within solenoid. This will open dump valve by
magnetic force created by solenoid coil.
Conditions for setting DTC:
* High voltage on EBCM solenoid driver circuit when expected to
be low (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0265: PUMP MOTOR RELAY CIRCUIT OPEN
Circuit Description
The relay supplies power to all 6 solenoid coils (3 isolation
solenoid coils and 3 dump solenoid coils) when ABS is required. The
relay and the 6 solenoid coils are located within the EBCM.
Conditions for setting DTC:
* EBCM microprocessor commands the relay on.
* Low voltage on all 8 solenoid driver circuits when all are
expected to high (solenoid not energized).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0266: PUMP MOTOR RELAY CIRCUIT SHORTED
Circuit Description
The relay supplies power to pump motor when ABS is required.
The relay is located within the EBCM.
Conditions for setting DTC:
* ANTI-LOCK indicator light check complete.
* High voltage on pump motor driver circuit when all are
expected to low (relay not commanded on).
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS fuse or fusible link. If fuse or fusible link
is open, go to step 9). If fuse or fusible link is okay, go to step
10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0267: PUMP MOTOR CIRCUIT OPEN (EXCEPT "L" & "M" SERIES)
Circuit Description
The pump motor circuit is integral to EBCM. The EBCM
energizes relay within EBCM to supply battery voltage to high side of
pump motor. When pump motor activation is required, EBCM grounds low
side of pump motor.
Conditions for setting DTC:
* EBCM internal relay on.
* motor off.
* Low voltage from low side of pump motor when expected to be
high.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin pump motor pigtail
connector from EBCM. Inspect connector and wiring for damage or
corrosion that could cause an open circuit between pump motor and
EBCM. If connector and wiring are okay, go to next step. If connector
or wiring is faulty, go to step 10).
3) Check resistance between terminals No. 1 and 2 of 2-pin
pump motor pigtail connector. If resistance is 0.1-0.3 ohm, go to step
15). If not, go to next step.
4) Disconnect 2-pin EBCM harness connector. Inspect connector
for damage or corrosion which could cause a loss of power to EBCM. If
connector is okay, go to next step. If connector is faulty, go to step
9).
5) Check resistance between ground and terminal No. 2 of 2-
pin EBCM harness connector. If resistance is 0-2 ohms, go to next
step. If not, go to step 11).
6) Turn ignition switch to RUN position. Check voltage
between ground and terminal No. 1 of EBCM harness connector. If
voltage reading is 10 volts or greater, go to step 8). If not, go to
next step.
7) Check ABS fuse or fusible link. If fuse or fusible link is
open, go to step 13). If fuse or fusible link is okay, go to step 14).
8) Inspect 2-pin EBCM harness connector for poor terminal
contact or corrosion. Check for open in ground circuit to EBCM. Repair
as necessary. Reconnect harness connectors. Using scan tool, clear
DTC. Test drive vehicle at speed greater than 10 MPH. If DTC C0267
resets as current DTC, go to step 12). If DTC does not reset,
malfunction is intermittent. See DIAGNOSTIC AIDS.
9) Repair 2-pin EBCM harness connector as necessary.
10) Repair 2-pin pump motor pigtail connector or wiring.
11) Repair open or high resistance in ground circuit to EBCM.
12) Replace EBCM.
13) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
14) Repair open or high resistance in battery circuit to
EBCM.
15) Replace BPMV assembly. After replacing assembly, perform
DIAGNOSTIC SYSTEM CHECK.
Diagnostic Aids
Pump motor is integral with BPMV assembly and cannot be
separately serviced. DTC C0267 can be caused by poor power and ground
at the 2-pin EBCM or 2-pin motor harness from the EBCM to the pump
motor. The EBCM or BPMV must be replaced if these tests show the pump
motor EBCM internal circuitry has failed.
DTC C0267: PUMP MOTOR CIRCUIT OPEN ("L" & "M" SERIES)
Circuit Description
The pump motor circuit is integral to EBCM. The EBCM
energizes the relay within EBCM to supply battery voltage to high side
of pump motor. When pump motor activation is required, EBCM grounds
low side of pump motor.
Conditions for setting DTC:
* EBCM internal relay on.
* Pump motor off.
* Low voltage from low side of pump motor when expected to be
high.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector and wiring for damage or corrosion that
could cause a loss of power to EBCM. If connector and wiring are okay,
go to next step. If connector or wiring is faulty, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage is reading is greater than 10
volts, go to step 8). If not, go to next step.
5) Check ABS fuse or fusible link. If fuse or fusible link is
open, go to step 9). If fuse or fusible link is okay, go to step 10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
Diagnostic Aids
Pump motor is integral with BPMV assembly and cannot be
separately serviced. DTC C0267 can be caused by poor power and ground
at the 2-pin EBCM or 2-pin motor harness from the EBCM to the pump
motor. The EBCM or BPMV must be replaced if these tests show the pump
motor EBCM internal circuitry has failed.
DTC C0268: PUMP MOTOR LOCKED OR PUMP MOTOR CIRCUIT
SHORTED (EXCEPT "L" & "M" SERIES)
Circuit Description
The pump motor circuit is integral to EBCM. The EBCM
energizes the relay within EBCM to supply battery voltage to high side
of pump motor. When pump motor activation is required, EBCM grounds
low side of pump motor.
Conditions for setting DTC:
* Vehicle speed at 8 MPH or greater.
* EBCM internal relay on.
* Pump motor commanded on and then off.
* High voltage from low side of pump motor for 100 milliseconds
when expected to be low.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin pump motor pigtail
connector from EBCM. Inspect connector and wiring for damage or
corrosion that could cause an open circuit between pump motor and
EBCM. If connector and wiring are okay, go to next step. If connector
or wiring is faulty, go to step 10).
3) Check resistance between terminals No. 1 and 2 of 2-pin
pump motor pigtail connector. If resistance is 0.1-0.3 ohm, go to step
15). If not, go to next step.
4) Disconnect 2-pin EBCM harness connector. Inspect connector
for damage or corrosion which could cause a loss of power to EBCM. If
connector is okay, go to next step. If connector is faulty, go to step
9).
5) Check resistance between ground and terminal No. 2 of 2-
pin EBCM harness connector. If resistance is 0-2 ohms, go to next
step. If not, go to step 11).
6) Turn ignition switch to RUN position. Check voltage
between ground and terminal No. 1 of EBCM harness connector. If
voltage reading is 10 volts or greater, go to step 8). If not, go to
next step.
7) Check ABS fuse. If fuse is open, go to step 13). If fuse
is okay, go to step 14).
8) Inspect 2-pin EBCM harness connector for poor terminal
contact or corrosion. Check for open in ground circuit to EBCM. Repair
as necessary. Reconnect harness connectors. Using scan tool, clear
DTC. Test drive vehicle at speed greater than 10 MPH. If DTC C0268
resets as current DTC, go to step 12). If DTC does not reset,
malfunction is intermittent. See DIAGNOSTIC AIDS.
9) Repair 2-pin EBCM harness connector as necessary.
10) Repair 2-pin pump motor pigtail connector or wiring.
11) Repair open or high resistance in ground circuit to EBCM.
12) Replace EBCM.
13) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
14) Repair open or high resistance in ground circuit to EBCM.
15) Replace BPMV assembly.
Diagnostic Aids
Pump motor is integral with BPMV assembly and cannot be
separately serviced. DTC C0267 can be caused by poor power and ground
at the 2-pin EBCM or 2-pin motor harness from the EBCM to the pump
motor. The EBCM or BPMV must be replaced if these tests show the pump
motor EBCM internal circuitry has failed.
DTC C0268: PUMP MOTOR LOCKED OR CIRCUIT SHORTED ("L" &
"M" SERIES)
Circuit Description
The pump motor circuit is integral to EBCM. The EBCM
energizes the relay within EBCM to supply battery voltage to high side
of pump motor. When pump motor activation is required, EBCM grounds
low side of pump motor.
Conditions for setting DTC:
* Vehicle speed at 8 MPH or greater.
* EBCM internal relay on.
* Pump motor commanded on and then off.
* High voltage from low side of pump motor for milliseconds
when expected to be low.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 6).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 7).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 8). If not, go to next step.
5) Inspect ABS 60-amp MAXI-fuse. If fuse is open, go to step
9). If fuse is okay, go to step 10).
6) Repair 2-pin EBCM harness connector as necessary.
7) Repair open or high resistance in ground circuit to EBCM.
8) Replace EBCM.
9) Repair short to ground in battery circuit between
underhood fuse/relay block and EBCM.
10) Repair open or high resistance in battery circuit to
EBCM.
DTC C0269 OR C0274: EXCESSIVE DUMP/ISOLATION TIME
Circuit Description
The EBCM microprocessor grounds the isolation coil to
energize and close the valve. This will prevent any additional brake
pressure applied by the driver from reaching the wheels. Each
isolation valve operates independently to isolate each wheel.
Conditions for setting DTC:
* Isolation time (pressure hold) exceeding 255 consecutive 1.0
second checks.
* Isolation time (pressure hold) exceeds 120 seconds.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition off. Disconnect 2-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 11).
3) Check resistance between ground and 2-pin EBCM harness
connector terminal "B". If resistance is 0-2 ohms, go to next step. If
not, go to step 12).
4) Check voltage between ground and 2-pin EBCM harness
connector terminal "A". If voltage reading is greater than 10 volts,
go to step 6). If not, go to next step.
5) Inspect ABS 60-amp MAXI-fuse. If fuse is open, go to step
13). If fuse is okay, go to step 14).
6) Turn ignition off. Disconnect 10-pin EBCM harness
connector. Inspect connector for damage or corrosion which could
result in loss of power to EBCM. If connector is okay, go to next
step. If connector is not okay, go to step 15).
7) Check resistance between ground and terminal J of 10-pin
EBCM harness connector. If resistance is 0-2 ohms, go to next step. If
not, go to step 16).
8) Turn ignition switch to RUN position. Check voltage
between ground and 2-pin EBCM harness connector terminal "A". If
voltage reading is greater than 10 volts, go to step 10). If not, go
to next step.
9) Inspect ABS 10-amp fuse. If fuse is open, go to step 17).
If fuse is okay, go to step 18).
10) Turn ignition off. Disconnect 10-pin and 2-pin EBCM
harness connector. Inspect connector for damage or corrosion which
could result in loss of power to EBCM. Repair any evident damage.
Reconnect all connectors. Clear all DTCs using the scan tool. Test
drive the vehicle above 10 mph. If DTC resets, go to step 19). If not,
malfunction is intermittent, see DIAGNOSTIC AIDS.
11) Repair 2-way EBCM connector.
12) Repair open or high resistance in ground circuits.
13) Repair short to ground in circuit No. 442.
14) Repair open or high resistance in circuit No. 442.
15) Repair the 10-way connector.
16) Repair open or high resistance in signal and power ground
circuits.
17) Repair short to ground in circuit No. 441.
18) Repair open or high resistance in circuit No. 441.
19) Replace the EBCM.
Diagnostic Aids
Repair any other DTCs first. Using the scan tool, perform the
Function test to ensure proper ABS operation.
DTC C0271, C0272 & C0273: EBCM INTERNAL FAULT
Circuit Description
The EBCM initializes a self-test when ignition switch is
turned to RUN position. The EBCM self-test verifies all internal
circuitry within the EBCM is operating correctly.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Using scan tool, attempt to clear DTCs. If DTCs cleared,
go to next step. If not, go to step 4).
3) Check for history DTCs and data. If this is the first time
DTC has set, perform DIAGNOSTIC SYSTEM CHECK. If DTC was set before,
go to next step.
4) Replace EBCM.
DTC C0281: STOPLIGHT SWITCH ALWAYS CLOSED OR SHORTED
Circuit Description
The stoplight switch is a normally closed switch. With
ignition switch in the RUN position and brake pedal not depressed,
ignition voltage will be present at the EBCM. When brakes are applied,
the ignition voltage at the EBCM will be zero.
Conditions for setting DTC:
* Vehicle speed greater than 35 MPH for 10 seconds followed by
vehicle at rest for one second.
* Stoplight switch never switching during the described
condition.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition on. Using scan tool, select DATA LIST
function. Check the status of the stoplight switch while applying and
releasing brake pedal. If scan tool indicates switch is closed (pedal
not applied) at all times, go to next step. If not, go to step 4).
3) Turn ignition off. Disconnect stoplight switch connector.
Turn ignition switch to RUN position. Using scan tool, check status of
stoplight switch. If scan tool indicates switch is closed (pedal not
applied), go to step 7). If not, go to step 8).
4) If scan tool indicates that switch is open (pedal applied)
at all times, go to next step. If not, go to step 7).
5) Turn ignition off. Disconnect 10-pin EBCM harness
connector. Turn ignition switch to RUN position. Using DVOM, check
voltage between ground and terminal "C" of 10-pin EBCM harness
connector. If voltage reading is greater than 10 volts, go to next
step. If not, go to step 8).
6) Turn ignition off. Reconnect all harness connectors. Turn
ignition switch to RUN position. Select DATA LIST function on scan
tool. Using scan tool, check status of stoplight switch while applying
and releasing brake pedal. If scan tool indicates switch is open
(pedal applied) at all times, go to step 9). If not, go to next step.
7) Malfunction is intermittent. See DIAGNOSTIC AIDS.
8) Repair faulty stoplight switch or open in stoplight switch
circuit between EBCM and stoplight switch.
9) Replace EBCM.
DTC C0286: ANTI-LOCK INDICATOR LIGHT CIRCUIT SHORTED TO
BATTERY VOLTAGE
Circuit Description
The ANTI-LOCK indicator light is powered by ignition voltage
through the GAUGE fuse. The EBCM output will be high (battery voltage)
when indicator light is off, and will be low (ground) when light is
on. If DTC C0286 sets, the EBCM will store the code in memory but will
not disable the ABS. If DTC C0286 is in memory and a different fault
occurs, EBCM will illuminate the BRAKE indicator light to notify
operator of the problem.
Conditions for setting DTC:
* High voltage on ANTI-LOCK indicator light circuit when
expected to be low (light commanded on).
* Anything that keeps the ANTI-LOCK indicator light circuit
high when light is supposed to be illuminated, such as a
short to voltage on ABS indicator light circuit between
instrument cluster and EBCM.
Diagnosis
1) Perform diagnostic system check. See DIAGNOSTIC SYSTEM
CHECK. After performing diagnostic system check, go to next step.
2) Turn ignition switch to RUN position and observe ANTI-LOCK
indicator light operation. If indicator light illuminates and then
turn off after 3 seconds, go to step 5). If not, go to next step.
3) Turn ignition off. Disconnect 10-pin EBCM harness
connector. Using a fused (3-amp) jumper wire, jumper terminal "B" of
10-pin harness connector to ground. Turn ignition switch to RUN
position. If ANTI-LOCK indicator light illuminates, go to step 6). If
not, go to next step.
4) Inspect jumper wire fuse. If fuse is blown, go to step 7).
If fuse is not blown, go to next step.
5) Malfunction is intermittent. Inspect all connectors and
harnesses for damage which may result in high resistance when
components are connected. See DIAGNOSTIC AIDS.
6) Replace EBCM.
7) Repair short to voltage in ANTI-LOCK indicator light
circuit between instrument cluster and EBCM.
Diagnostic Aids
DTC C0286 is typically set by a shorted ANTI-LOCK indicator
light, although it can be set from a short to voltage in the circuit
between indicator light and EBCM, or a faulty EBCM.
DTC C0288: BRAKE WARNING LIGHT CIRCUIT SHORTED TO BATTERY
VOLTAGE
Circuit Description
The BRAKE warning light is powered by ignition voltage
thr

Thanks for that big ol book of info! I will look it over and see what I can find out. The problem though is that I still have no DTC's when I scan for them. Another wierd thing about this is that sometimes, my scanner will hang and it wont even get into the codes until I unhook the battery and reset the computer(s)... I guess it could be that there is one there that I cant scan for with my scanner, but I think the OTC setups are supposed to do it...