Sensor Question

[Hog Caller]

I have a 1989 Honda Prelude SI, 5 speed, 2.0, FI, DOHC, that will not start. The LED in the ECU gives a error code of 13, Atmospheric Pressure (PA) Sensor circuit. I have looked everywhere and can not find this sensor. There is a MAP sensor in the control box on the firewall, but no PA sensor. Does anyone know where it is? Or, do I really have one?
I need help!
Thanks.

[BIAR]

I would check for fuel and spark while cranking first.I have never seen a no start for a baro sensor.Carl

[ludegurl]

Originally Posted by Hog Caller

I have a 1989 Honda Prelude SI, 5 speed, 2.0, FI, DOHC, that will not start. The LED in the ECU gives a error code of 13, Atmospheric Pressure (PA) Sensor circuit. I have looked everywhere and can not find this sensor. There is a MAP sensor in the control box on the firewall, but no PA sensor. Does anyone know where it is? Or, do I really have one?
I need help!
Thanks.

Code 13 is BARO Sensor (barometric presure)

It should be right next to the MAP sensor. Your best bet is to go to a dealer and pretend youre buying a BARO sensor so you can see what it looks like and maybe ask them to show you the location.

Your baro sensor is sending an out of range signal to your ECU. That false signal could cause ECU to shut down your enjectors, therefore your engine will not start.

Diagnostic Trouble Code Identification


0
Engine Control Module
1
HO2S Or O2S
2
HO2S Or O2S{2}
VSS{1}
3
MAP Sensor
4
CKP Sensor{2}
Vacuum Switch{1}
5
MAP Sensor
6
ECT Sensor
7
TP Sensor{2}
M/T Clutch Switch Signal{1}
A/T Shift Position Signal{1}
8
TDC{2}
Ignition Coil Signal{1}
9
No. 1 Cylinder Position Sensor
10
IAT Sensor
12
EGR System
13
BARO Sensor
14
IAC Valve{2}
EACV{1}
15
Ignition Output Signal
16
Fuel Injector System
17
VSS
19
Lock-Up Solenoid Valve
20
Electric Load Detector
21
VTEC Solenoid Valve
22
VTEC Pressure Switch
23
KS
30
A/T FI Signal A
31
A/T FI Signal B
41
HO2S Heater
43
Fuel Supply System
48
HO2S{3}

[Hog Caller]

Thank you both for your help.

Halleluiah, I found it. My atmospheric pressure sensor is located under the dash, near the glove box and the ECU. A new sensor cleared my #13 error code and fixed half my problem.

I still have an error code 15, Ignition Output Signal, and the engine still will not start. Voltages at the Igniter unit check OK per the Troubleshooting Flow Chart in my Honda Service Manual.

The error code 15 only shows after cranking the engine. After resetting the ECU, the error codes does not show again when the ignition switch is turned on, only after the engine is cranked. The troubleshooting flow chart says: “Intermittent failure, test drive may be necessary.” I surely would like to do a test drive, but the engine will not run.

Does anyone have any suggestions?

Thanks.

[ludegurl]

Originally Posted by Hog Caller

Thank you both for your help.

Halleluiah, I found it. My atmospheric pressure sensor is located under the dash, near the glove box and the ECU. A new sensor cleared my #13 error code and fixed half my problem.

I still have an error code 15, Ignition Output Signal, and the engine still will not start. Voltages at the Igniter unit check OK per the Troubleshooting Flow Chart in my Honda Service Manual.

The error code 15 only shows after cranking the engine. After resetting the ECU, the error codes does not show again when the ignition switch is turned on, only after the engine is cranked. The troubleshooting flow chart says: “Intermittent failure, test drive may be necessary.” I surely would like to do a test drive, but the engine will not run.

Does anyone have any suggestions?

Thanks.

ok so youre almost there. check your camshaft and crankshaft sensors. they provide signal that activate your igniter unit.

[Hog Caller]

I checked the TDC and the Crank sensors per the service manual. They both have the proper resistance, 900 ohms. I verified continuity and no ground of all wires to the ECU.

[ludegurl]

Originally Posted by Hog Caller

I checked the TDC and the Crank sensors per the service manual. They both have the proper resistance, 900 ohms. I verified continuity and no ground of all wires to the ECU.

ok so you have continuity. now check if they are getting power when you turn key on engine off. if ok then check the signal wire (blue wire on the negative side of the ignition coil) and see if youre getting any fluctuating voltage when you crank your engine. this is the signal needed by your ignition coil to fires up your sparkplugs.

3 basic things needed to run an engine: fuel, compression and spark. if one of them is missing, your engine will not run.

my question is...what happened before your engine quit running? did your engine just quit running by itself or did you do any repair and mess up something?

[Hog Caller]

Engine started running very rough and then quit while driving. There is no pulsating voltage in the blue wire from the ingiter to the coil. For more details see the thread "Ignition Output Signal" in the "Lets Get Technical" forum.

[llllllllll]

Originally Posted by Hog Caller

Engine started running very rough and then quit while driving. There is no pulsating voltage in the blue wire from the ingiter to the coil. For more details see the thread "Ignition Output Signal" in the "Lets Get Technical" forum.

So there you go, ignition system is your problem. just like Ludegurl said, you need to find out why youre not getting any pulsating voltage on your negative teminal ignition coil while youre cranking your engine. sensors and igniter must be working to get pulsating voltage. dont buy the parts til you find out why.

[Hog Caller]

Have checked the TDC, Crank, and Cyl sensors per Honda service manual.

With an oscilloscope attached to the connecting white wire between the ECU and Ingiter, and the engine spinning, a constant positive 10.5 volts was observed. There was no cyclic voltage drop to trigger the igniter. Same test with no connection from the ECU to the igniter gave the same results.

Is a good igniter, connected to the ECU, required to see the pulsating output of a properly functioning ECU on an oscilloscope?

[JDMgirly]

Originally Posted by Hog Caller

Have checked the TDC, Crank, and Cyl sensors per Honda service manual.

With an oscilloscope attached to the connecting white wire between the ECU and Ingiter, and the engine spinning, a constant positive 10.5 volts was observed. There was no cyclic voltage drop to trigger the igniter. Same test with no connection from the ECU to the igniter gave the same results.

Is a good igniter, connected to the ECU, required to see the pulsating output of a properly functioning ECU on an oscilloscope?

While your engine is being cranked, the positive side of the ignition coil will give you constant voltage and the negative side of the coil will give you pulsating voltage.

Using your DSO (osciloscope) set it to wave form and check the signal output of your CMP and CKP sensors. do this while your engine is being cranked. Your sensors are faulty if you dont see any squarewaves on your DSO.

[Hog Caller]

Have checked the sensors and found them to give a good voltage signals to the ECU. The fundamental problem is that there is no pulsating negative voltage from the ECU to the igniter.

[hontoy]

Originally Posted by Hog Caller

Have checked the sensors and found them to give a good voltage signals to the ECU. The fundamental problem is that there is no pulsating negative voltage from the ECU to the igniter.

theres no such thing as negative pulsating signal from ECU to the igniter. its all positive pulsating signal and it comes from sensor to igniter then to ECU and back to igniter again.

the function of the igniter is to turn on and off the igition coil from ground to negative side of the coil. the function of the ECU is to control the ignition timing, it advance or retard the timing depending on the engine load, speed and temperature etc..

from my experience ive never seen a bad ECUs and so I doubt if ECU is the problem. They usually dont break unless you screw up by using a test light for troubleshooting.

read your manual over and over and make sure you understand how ignition system works. could be just a simple thing like loose wiring connections and they are hard to find.

if you really think your ECU is bad, try this wrecking yard link. Any ECU cost about $30 if you go pull the parts yerself. i think you can order the parts by phone but itll cost you more.

ecology auto wrecking