C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

service engine light with C12

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Old Feb 23, 2023 | 12:45 PM
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Default service engine light with C12

I have a battery drain issue (separate thread, stops when I pull the ccm2 fuse) so I've been disconnecting the battery during testing.
Now I have the service engine light on (after a few miles of driving) but checking the codes is clear - only C12 and no history. Car seems to run fine. I do know that I have a catalytic convertor issue detected via the smell.
What do I do now?

Does a regular ODBII reader show anything else on a 1996 that's not displayed on the dash diagnositcs?


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Old Apr 25, 2023 | 11:54 PM
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I had an old ELM327 with usb connector but didn't find a phone app that supports it. (suggestions?)
I got a wifi one and it came up with 2 codes (misfire and a too lean code). Service light has gone off so I think (hoping) these were just stray codes.
So it seems that there are codes that are not picked up by the internal computer and the dash display. Just looking for confirmation.

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Old Apr 26, 2023 | 04:42 AM
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Originally Posted by IHBD
See this thread from yesterday. Another 96 owner attempting to pull ECM codes with the onboard diagnostics.


I speculated in that thread that the diagnostics don't communicate with the OBD II 1996 ECM, so engine codes aren't available in 1996 on the 'dash display'. In the other thread, the OP indicates that he does not see Module 4. Which is the ECM. When you see C12 in Module 1, what is the next Module? If it is 7 or 9, it 'skipped' Module 4, probably because the OBD II isn't supported for 96.

There are several peeps here that will tell you I know squat about these cars. I wish one of them that knows the 96 would chime-in on the "Does the 96 support Module 4 in the onboard diagnostics" question. I'm curious. And there are two owners currently wondering the same thing about their 96s.
A '96 FSM indicates that Module 4 'should be available'
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Old May 3, 2023 | 03:32 PM
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The dash diags have modules 1, 9 and A.

The service engine soon light has gone out but I still get the codes when I hook up the ODB II. So I was surprised about that. I tried clearing it with the ODB software but codes still show. Bad software (Torque Light, until I know what to expect) or something else?
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