Jose Quintanilla

I need some help with my 1994 C4 71k miles, I知 new with Corvettes. The car runs fine but this happened to me 5 times already, it dies then I have to wait 2 to 4 minutes then it runs fine for other 30 to 40 minutes, I知 reading the codes and this is what I have.

Module 1 CCM
C81
H81

Module 4 ECM
Err

Module 9
C24
H24

I really appreciate any help
Thanks

Cliff Harris

Check out this link:

https://www.corvetteforum.com/forums...post1576116036

pcolt94

You need specific information from a 94 FSM. Generic info like from a 93 and others won't due. And almost nobody posts Module 1 codes, everybody is concerned with the ECM/PCM in module 4.

Module 1, code 81- Invalid vehicle configuration detected. In short, it's a possible serial data (bus) problem or things on the bus not matching.

Module 4 - Err - This is not normal where the CCM should be communicating with the PCM for any codes. Normal for no codes will be 3 dashed lines.

Module 9 - The Code 24 is not in my 94 FSM book. It might be an error in the display of it. The brake computer has to be cleared using the CCM and trip monitor buttons. (But if the CCM is not working it may not be possible)

All in all these indications are not healthy and all of them indicate a problem with the data bus, CCM or some kind of communication problem between the modules. None of these codes relate to the running of the engine as those codes would be in module 4.

The CCM does need to communicate with the PCM for fuel (FEDS) and spark. VATS happens in the CCM which enables you the turn over the engine. There are obviously other communications that make many more things work correctly.

I would start disconnecting the battery for a minute and check for codes and see if anything changes. If it does not, then you need a plan of attack. Possible bad connection, CCM or bad module on the bus just for a few ideas.

Jose Quintanilla

***************
Thanks for your response, very clear.
I already tried resetting the codes disconnecting the battery, also using the trip/Odo

For CCM 1.7
For ECM 4.7
For ABS 9.7
For DERM A.7

Then Eng/Met, I see the --- but next time I try to read the codes, the same codes are there.
I知 thinking on replacing the ECM for this one from Autozone,
https://www.autozone.com/engine-mana...44103_481624_0

looks like is ready to swap,
of do you recommend any other with better performance ?

Thanks again

pcolt94

That痴 a gambol and an leap of faith. I would not go that path before I did more testing.

Are you sure that is the right part? There's a difference between PCMs if they are for automatic or manual transmissions. Also I would not let my OEM PCM out of my control (giving it up for the core charge) before I went into the unknown with another one and not knowing it would fix it.

I would try to eliminate items by process of elimination to try to get a handle on the root of the problem.
Pull fuse 33 for the PCM to get it out of the equation. See if module 1 gives a valid no code indication of 3 bars. Do the same with the brake computer.

I think the CCM is the heart and control of all the diagnostics and codes. I would see if I could get it to respond correctly. There's an equal chance the problem could be the CCM as well but that痴 a guess and just a possibility.

fake

When was the opti replaced or the water pump? Are the hoses new for cooling? Does it back fire when warm? Before doing major work get the history of the car. Check ignition coil for dirt grime contact etc. My C4 had a different code every other day when i pulled the water pump the shaft barely moved and the opti had so much rust and corrosion in it i do not know how the car started.

Jose Quintanilla

Sorry for taking a long time for my reply
I bought the car 4 months ago, I think the opti and pump are original. Not sure.
I disconnected the ECM for few days, check the connectors, and everything looks fine,
I replaced the spark plugs, just in case and they were ok, then drove the car for like an hour,
I Still getting these codes, i'm concern about the Err on the ECM, Thanks

Module 1 CCM
C81
H81

Module 4 ECM
Err

Module 9
---

A
H24