Fault codes

[hakogen]

I've been wracking my brain on this one forever guys... as a matter of fact this might have been my first thread way back in the day. Even if you don't know, feel free to share in my confusion.

p0179
fuel compensation sensor circuit, low input
p0178
high input

these two codes come and go mysteriously. truck runs fine, doesnt leak anything, no blown fuses/relays, fuel pump works fine (to date) any ideas?

01, 2.2, 2wd, 5sp, std cab.

[hakogen]

does anyone out there have a 99-03 s-10 2.2 that has the MIL (check engine lite) come on and off at inopportune times?

[dmbrisket 51]

my 98 (same computer) hasnt throwen a code at, specally not at random times

[BlazerLT]

That is the sensor that indicates what kind of fuel you are putting in the vehicle.

As far as we can determine the sensor is on the right side frame rail, it supposedly has two fuel lines in and an electrical wire coming out.

DTC P0178
Circuit Description
Alcohol content information is supplied to the powertrain control module (PCM) from the fuel composition sensor (FCS). The FCS measures fuel temperature through an internal thermistor. The fuel conductivity and capacitance are electronically measured inside a small fuel cell. The internal circuitry combines the electrical measurement and fuel temperature information using a microprocessor to produce a Hertz frequency output.

Conditions for Running the DTC
The engine run time is more than 30 seconds.
The ignition voltage is more than 10.9 volts.
Conditions for Setting the DTC
The FCS frequency is below 45 Hz for 12.5 seconds.

Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
The Hertz (Hz) and millisecond (ms) parameters on the scan tool react immediately to any change of state in the ground or signal circuits. Hz and ms may show a change, but the change may not occur long enough to set the code. Watch Hz and ms to identify intermittent problems in the signal circuit. An intermittent fault in the signal circuit will immediately change the Hz and ms parameters. The Freeze Frame/Failure Records may be used to reproduce conditions at the time of the failure. A reading of 16 Hz in the Freeze Frame/Failure Records indicates a circuit fault occurred.

The ignition positive voltage circuit needs the fault to occur a longer period of time to affect the sensor output. An intermittent fault here may not show up by looking at Hz or ms because the sensor does not immediately power down and the connection may be restored before voltage drops below the operating threshold, such as a loose terminal. If the DTC will not reset and Hz and ms are steady, thoroughly inspect all FCS circuits while paying close attention to the ignition positive voltage circuit wire and or terminals for an intermittent open.

The J 44175 Fuel Composition Tester can be used to check the accuracy of the sensor if a fault is not isolated using this table. If the Fuel Test is performed before the electrical circuits have been tested using this table, the results will be in error.


Important
Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.


The following may cause an intermittent:

Mis-routed harness
Rubbed through wire insulation
Broken wire inside the insulation
Poor terminal contact
Test Description
The numbers below refer to the step numbers on the diagnostic table.

This step verifies that a fault is present.

This step is looking for a reference voltage from the PCM. An excessively high or low voltage is an indication of a problem with the circuit, or a malfunctioning PCM.

[BlazerLT]

DTC P0179
Circuit Description
Alcohol content information is supplied to the powertrain control module (PCM) from the fuel composition sensor (FCS). The FCS measures fuel temperature through an internal thermistor. The fuel conductivity and capacitance are electronically measured inside a small fuel cell. Internal circuitry combines the electrical measurement and fuel temperature information using a microprocessor to produce a Hertz frequency output.

Circuitry inside the sensor provides a default output of 170 Hz if the fuel conductivity is too high or an internal fault is detected. A test of the fuel must be made to determine the cause of the 170 Hz output.

Conditions for Running the DTC
The engine run time is more than 30 seconds.
The ignition voltage is more than 10.9 volts.
Conditions for Setting the DTC
The FCS frequency is more than 155 Hz for 12.5 seconds.

Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Diagnostic Aids
The Hertz (Hz) and millisecond (ms) parameters on the scan tool react immediately to any change of state in the ground or signal circuits. Hz and ms may show a change, but the fault may not occur long enough to set the code. Watch Hz and ms to identify intermittent problems in these two circuits.

The ignition positive voltage circuit needs a hard fault to set a code. An intermittent fault here may not show up by looking at Hz or ms. If the diagnostic trouble code (DTC) will not reset and Hz and ms are steady, thoroughly inspect all FCS circuits while paying close attention to the ignition positive voltage circuit wire and or terminals for an intermittent open.


Important
Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.


The following may cause an intermittent:

Mis-routed harness
Rubbed through wire insulation
Broken wire inside the insulation
Poor terminal contact
Test Description
The numbers below refer to the step numbers on the diagnostic table.

This step checks for a frequency that is out of range or intermittent at the time of the test .

This step determines if the intermittent high frequency is due to water droplets passing through the sensor.

This step compares the reading from the fuel composition sensor with an external test tool to determine the accuracy of the vehicle sensor and the compatibility of the fuel in the tank.

[hakogen]

blazer, you are a god among men. thanks a million. where did you get this info from?

[BlazerLT]

Super secret

Have to kill you if I told you.

[dmbrisket 51]

Originally Posted by BlazerLT

Super secret

Have to kill you if I told you.

Im willing to take the chance, your in canida and im just outside Detroit, not like the two are connected through a tunnel or anything

[rlith]

Originally Posted by dmbrisket 51

Im willing to take the chance, your in canida and im just outside Detroit, not like the two are connected through a tunnel or anything

www.alldata.com

[dmbrisket 51]

lol that was my guess but wasnt 100% sure

[BlazerLT]

Originally Posted by dmbrisket 51

lol that was my guess but wasnt 100% sure

Please remove you large signature for me.