Hey guys,
I have a 1994 C4 vette that I purchased off of someone who really didn't know what he was doing. I got the Corvette in boxes. The LT1 was partially torn down. I ended up sending it off and had the whole thing rebuilt professionally, including a new opti (not cheap). I got it back, put it in, did the wiring, but I am not getting signal to the ICM B wire. I do have firing injectors, so I know the Opti is sending its signal. I am just not getting signal from the PCM.
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I have ran the wires back to the PCM and looked over the grounds and the harness in general, but I haven't gotten anywhere. I cant get Fire.
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What do you guys think? I can't get my OBDII cable to work and I figure its because its not OBDI Compatible. So, I can't flash the PCM. Could the PCM be bad? Anyone in Central Oklahoma willing to help me test this theory? I'll buy you some beer...

 

Does "service engine soon" light work and do you have any codes stored? You should be able to use on board to display codes. Do you have Factory Service Manual with drivability electrical sections? Being the was a "basket case" you need to verify all grounds are clean, tight and in correct location. Along with powertrain connectors are properly seated and are not corroded. With a noid light with the injector connectors blink? If not I think you need to verify opti and connector/ jumper to it. Are you getting correct voltage on terminals at B2, 3, 14 and 20 of PCM? If you are then opti and wiring to pcm should be ok If you disconnect ICM and PCM you could use A DVOM to test white wire from term B5 to ICM term B for high resistance and short to ground or voltage. You now maybe faced with the original condition why the car was taken apart.

 

From the Top: The SES light is on. I did have some stored codes, but majority of them are from Module 9. The one code I got from Module 4 was C15, which makes sense, because I haven't put the radiator back in... There is no room with it in to work on it. I do not have the FSM but I have been using online resources in attempts to track it down. I found a bad ground at the rear of the motor that goes by the battery, and I fixed that issue. The injectors are flashing while turning over. I haven't attempted to see if the PCM was getting voltages at the B2,3,14, or 20. Could you let me know which ones those are? I have taken the wrapping off of the Harness from the ICM to PCM. There are no broken wires nor frays. The wrapping was pretty bad, so I am going to get some more.

I am under the assumption this is the reason why the guy was trying to swap heads with his "Race Trans Am" before giving up on the ordeal. I do have an extra LT1 that I pulled from a 1993 Trans Am, but sadly, the PCM is an older connector type.

At this point, I have been 'spinning my wheels'. I am under the assumption that the PCM is getting power, since it does communicate. Its the ignition circuit that isn't getting signals... Frustrating.

Thanks for the help!

 

With no book you are limited. If you can find a used 94 LT1 PCM it doesn't necessarily have to be for a Corvette. If it's for/from a Roadmaster, Fleetwood, Caprice or "F" body it would worth substituting. I would look for a wreck because odds are it was running when the crash occurred. Pick & Pull type yards are normally pretty cheap. Your are just trying to see if it will start. If it will then you can get it reprogrammed for Corvette.

 

I have the Mitchell's on-demand. But I have limited use of it.

I know of a Corvette salvage nearby that I could go and see if they have any PCMs.... Thanks for the heads up.

At this point, I don't have much else to work with...

 

I have a 1995 PCM, not 100% sure they are the same though.