1994 C4 ICM Fire Problem
Thread Starter
3rd Gear
Joined: Mar 2016
Posts: 3
Likes: 0
1994 C4 ICM Fire Problem
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...
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.
~~
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.
~~
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...
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
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.
Thread Starter
3rd Gear
Joined: Mar 2016
Posts: 3
Likes: 0
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.
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!
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
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.
Thread Starter
3rd Gear
Joined: Mar 2016
Posts: 3
Likes: 0
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 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...
7th Gear
Joined: Jan 2010
Posts: 7
Likes: 1
I have a 1995 PCM, not 100% sure they are the same though.
