Check Engine light but C12 code??
Thread Starter
Instructor
Joined: Sep 2004
Posts: 139
Likes: 3
From: Rockland County NY
Check Engine light but C12 code??
1996, 50K miles.
After reading about the DTC codes today, I got home and shorted the OBD connector pins 4&12 and all I got was a C12 code - nothing stored - but my check engine light is still on even after clearing (though there was nothing to clear!).
What's next?
Other info - the PKE light is always on as that system sent bad on my last year and I disabled it. I'm hoping to replace the PKE computer soon but its not on my priority list. Car is running fine.
After reading about the DTC codes today, I got home and shorted the OBD connector pins 4&12 and all I got was a C12 code - nothing stored - but my check engine light is still on even after clearing (though there was nothing to clear!).
What's next?
Other info - the PKE light is always on as that system sent bad on my last year and I disabled it. I'm hoping to replace the PKE computer soon but its not on my priority list. Car is running fine.
Burning Brakes
Joined: May 2006
Posts: 1,097
Likes: 2
From: Richfield Utah
Originally Posted by barry96
1996, 50K miles.
After reading about the DTC codes today, I got home and shorted the OBD connector pins 4&12 and all I got was a C12 code - nothing stored - but my check engine light is still on even after clearing (though there was nothing to clear!).
What's next?
Other info - the PKE light is always on as that system sent bad on my last year and I disabled it. I'm hoping to replace the PKE computer soon but its not on my priority list. Car is running fine.
After reading about the DTC codes today, I got home and shorted the OBD connector pins 4&12 and all I got was a C12 code - nothing stored - but my check engine light is still on even after clearing (though there was nothing to clear!).
What's next?
Other info - the PKE light is always on as that system sent bad on my last year and I disabled it. I'm hoping to replace the PKE computer soon but its not on my priority list. Car is running fine.
Think I'll watch this post if ya don't mind? 
Thread Starter
Instructor
Joined: Sep 2004
Posts: 139
Likes: 3
From: Rockland County NY
bogus - Is the OBD2 reader and it's reset ability is better than the built in diagnostics run from the dash buttons? It doesn't seem like the control module would fail and set the light while still work correctly displaying the codes on the speedometer in diagnostic mode. Is it possible that there is some short that turns this light on?
Is there a separate module that controls the display of the diag lights? I guess it's back to the manuals but I don't have much spare time for the next couple days. Work just gets too limiting sometimes<g>.
Is there a separate module that controls the display of the diag lights? I guess it's back to the manuals but I don't have much spare time for the next couple days. Work just gets too limiting sometimes<g>.
Last edited by barry96; Jun 6, 2006 at 08:41 AM.
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
Your 96 is OBDII. The 94 and 95's had the OBDII connector but were still OBD1.
To read the PCM DTC codes on a 96 you need a OBDII reader.
If the Service Engine Soon light is on, that does indicate the PCM has detected a problem.
To read the PCM DTC codes on a 96 you need a OBDII reader.
If the Service Engine Soon light is on, that does indicate the PCM has detected a problem.
Racer
Joined: Jan 2005
Posts: 418
Likes: 45
From: Houston Texas
Originally Posted by Hooked on Vettes
Your 96 is OBDII. The 94 and 95's had the OBDII connector but were still OBD1.
To read the PCM DTC codes on a 96 you need a OBDII reader.
To read the PCM DTC codes on a 96 you need a OBDII reader.
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Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by bogus
take it to the local autozone and have them scan the computer for codes... their machine should also clear them.
they should be able to pull the code for free. They have the scanner for 96 and up... OBDII
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
Originally Posted by DMGroh
That's what I thought until corrected by SkateboardDave. Do a search of him or me within the past month or so and you'll find a post you'll want to print and save.
From your response, Module 4 (PCM/ECM) error codes were not displayed. All of the other Modules
CCM, ABS and Derm were displayed when you shorted 12 to 4.
In my response to this post I mentioned you can't read PCM codes on a 96 without a code reader. (You could read the PCM code if you had the proper scanning software).
I'm not sure why GM didn't allow you to check PCM codes by shorting pin 12 to 4. Someone did mention it could be because the Speedometer display doesn't have the capability of displaying enough digits.
Thread Starter
Instructor
Joined: Sep 2004
Posts: 139
Likes: 3
From: Rockland County NY
Update
I was going get into this more this past weekend but the darn thing just turned itself off! So I'm not going to try and track down this ghost. The only thing I can think of is that I tightened the gas cap (after reading some other posts). But shouldn't something have been recorded in the OBD system is the light ever goes on?
Oh well.
Now I have a more serious problem - the water pump seems to be lightly spraying antifreeze around. This is not good.
Oh well.
Now I have a more serious problem - the water pump seems to be lightly spraying antifreeze around. This is not good.
