91 code decoding
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Joined: Dec 1999
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From: Harrison Twp MI
91 code decoding
Hello,
I have a 91 and it is displaying codes c12 (ccm) and h32/34 (pcm).
I cannot find a cross-reference for c12...can anyone point me to the proper source/answer.
Also is the combination of h32/34 common and point to the egr?
Thanks.
Jeff
I have a 91 and it is displaying codes c12 (ccm) and h32/34 (pcm).
I cannot find a cross-reference for c12...can anyone point me to the proper source/answer.
Also is the combination of h32/34 common and point to the egr?
Thanks.
Jeff
Le Mans Master
Joined: Jul 2002
Posts: 5,818
Likes: 2
From: Alive and well in Burlington NC
Is the SES light on?
Code C12 is just a check code. H32 is a history code. At some point the EGR circuit returned an error (not uncommon). H34 (also history) is strange since it relates to the Mass Air Flow (MAF) sensor which you shouldn't have on your 91. I don't have my manual at work, but it might be manifold air pressure related. Anyway, since they are history codes, I'd clear them and see if they reappear.
Hope this helps.
Code C12 is just a check code. H32 is a history code. At some point the EGR circuit returned an error (not uncommon). H34 (also history) is strange since it relates to the Mass Air Flow (MAF) sensor which you shouldn't have on your 91. I don't have my manual at work, but it might be manifold air pressure related. Anyway, since they are history codes, I'd clear them and see if they reappear.
Hope this helps.
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Joined: Dec 1999
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From: Harrison Twp MI
Thanks.
The SES light was going on and off frequently during a 200 mile trip yesterday.
It stayed on the last few miles and the car ran bad...could not get power and rpms above 2500.
It is not on now...but the car is running real rough.
When it was going on/off the car ran fine...just the last time it starting running bad.
Now I did get about 10 gallons of fuel to top the tank. I would think if I had water it would be running bad all the time???
Thanks.
Jeff
The SES light was going on and off frequently during a 200 mile trip yesterday.
It stayed on the last few miles and the car ran bad...could not get power and rpms above 2500.
It is not on now...but the car is running real rough.
When it was going on/off the car ran fine...just the last time it starting running bad.
Now I did get about 10 gallons of fuel to top the tank. I would think if I had water it would be running bad all the time???
Thanks.
Jeff
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
The code 34 can be either MAF reading too low or MAP reading too low.
Since the SES is intermittent, open the connecor in the Orn wire near the battery for about 1 minute to clear stored codes. Then, when the SES comes on again, pull the current codes.
There is an EGR diagnostic method on my site that uses commonly available instruments.
Since the SES is intermittent, open the connecor in the Orn wire near the battery for about 1 minute to clear stored codes. Then, when the SES comes on again, pull the current codes.
There is an EGR diagnostic method on my site that uses commonly available instruments.
LS/MFT
Joined: Jun 2000
Posts: 5,874
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From: Cary IL
St. Jude Donor '09-'10-'11-'12
Jeff,
Saw your post on the yahoo c4 forum and responded to you by email. There you said that you had a 32/45. A 32/34 on a '91 indicates EGR circuit/MAP circuit (signal voltage low - high vacuum). Based on your posting of 32/45, I said the problem was most likely a faulty EGR solenoid, but if you're showing a 32/34, it is more likely the MAP (located on the right side of the intake plenum, top, to the rear). The EGR and MAP do not share any circuits, so it is unlikely an electrical problem (short or ground). The MAP uses an algorithm to tell the ECM what the manifold pressure is. Code 32 will set when either:
* Engine running less than 1200RPM
* Signal too low for 1 second
OR
* Engine running greater than 1200RPM
* Throttle posistion > 10%.
* Signal is too low for 1 second.
The EGR circuit (from the ECM) uses air flow (vacumm) along with coolant temp and engine RPM to activate the EGR via the EGR solenoid. If the MAP sensor has failed (as common as the EGR solenoid failure) the ECM is getting faulty air flow information and could set both a 32 and 34. BTW, a 45 indicates a faulty O2 sensor.
Unless you want to throw parts at it, email me and I'll send you the test pages form the service manual so you can replace the right parts.
Jac
Saw your post on the yahoo c4 forum and responded to you by email. There you said that you had a 32/45. A 32/34 on a '91 indicates EGR circuit/MAP circuit (signal voltage low - high vacuum). Based on your posting of 32/45, I said the problem was most likely a faulty EGR solenoid, but if you're showing a 32/34, it is more likely the MAP (located on the right side of the intake plenum, top, to the rear). The EGR and MAP do not share any circuits, so it is unlikely an electrical problem (short or ground). The MAP uses an algorithm to tell the ECM what the manifold pressure is. Code 32 will set when either:
* Engine running less than 1200RPM
* Signal too low for 1 second
OR
* Engine running greater than 1200RPM
* Throttle posistion > 10%.
* Signal is too low for 1 second.
The EGR circuit (from the ECM) uses air flow (vacumm) along with coolant temp and engine RPM to activate the EGR via the EGR solenoid. If the MAP sensor has failed (as common as the EGR solenoid failure) the ECM is getting faulty air flow information and could set both a 32 and 34. BTW, a 45 indicates a faulty O2 sensor.
Unless you want to throw parts at it, email me and I'll send you the test pages form the service manual so you can replace the right parts.
Jac
