1991 with Unknown Electrical Issues
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Heel & Toe
Joined: Jun 2013
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From: California
1991 with Unknown Electrical Issues
I had an earlier tread on trying to figure out how to get replacement keys (without knowing the VAT key code since the dealership did not have it). I decided to start a new thread here to focus on a way to diagnose the 'Vette. I do not know its history, so that is another layer of obscurity.
I have a 1991 6-speed. It does not start. When I short the A-B pins on the diagnostic connector, I get a 4-6 code. I disconnected the VATs connector that goes to the ignition and tried all the different resistance values, but they did not work. There was an ECM installed (re-manufactured weatherproof version), and another loose in the car (non-stock 01227727), so some electrical issue was being worked on at one time.
One ECM (non-stock 01227727) gives me the 4-6 error code, the other does not blink at all. I am wondering if the ECM has the correct EEPROM chip in it. I am also wondering if the BCM is working properly.
Other notes: When I turn the ignition to the "start" position, the radiator fan(s) go on. The radio does not turn on. The dash LED and security light do not work.
I have a 1991 6-speed. It does not start. When I short the A-B pins on the diagnostic connector, I get a 4-6 code. I disconnected the VATs connector that goes to the ignition and tried all the different resistance values, but they did not work. There was an ECM installed (re-manufactured weatherproof version), and another loose in the car (non-stock 01227727), so some electrical issue was being worked on at one time.
One ECM (non-stock 01227727) gives me the 4-6 error code, the other does not blink at all. I am wondering if the ECM has the correct EEPROM chip in it. I am also wondering if the BCM is working properly.
Other notes: When I turn the ignition to the "start" position, the radiator fan(s) go on. The radio does not turn on. The dash LED and security light do not work.
Advanced
Joined: Jun 2013
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From: Junction City Oregon
I'm new to this but have learned a lot from members on this forum. I had similar problems with my 1990 vert six speed. When I purchased it, it was non operational with the same problems you have, someone had disassembled it and replaced this and that. It came with extra ECM, CCM, prom chip, and extra gauge assembly. Nothing worked, including certain parts of the instrument panel, so I decided to get back to original. I sent the original CCM to Davies Corvette in Florida and had it reprogrammed, installed the original ECM with the original prom. Since I did not know what the original CCM had in it for resistance code to correspond with the ignition key, I asked Davies Corvette to program the CCM with Key Code #7 and then bought two ignition keys code #7 from Ecklers Corvette and had them cut to the original key so they would fit. It takes around two weeks for the CCM to return, so while I was waiting I checked out the entire wiring harness. Once I got the CCM back from being reprogrammed, the car started right up. My problem in the beginning was, I didn't have much of an idea of what the previous owner had done, so I had to pretty much start from scratch. I hope this helps you.
Drifting
Joined: May 2013
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From: Reno Nevada
Open the ecm and tell me what the alpha code is on the memcal? IE: AXCN
You can also have the VATS programmed out and save all that extra work.
You can also have the VATS programmed out and save all that extra work.
Last edited by MrWillys; Jul 22, 2013 at 05:12 PM.
Thread Starter
Heel & Toe
Joined: Jun 2013
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From: California
Uncle Phippy, good suggestions... A rebuilt CCM/BCM looks a little pricey. Is there any way to tell if the BCM is bad from doing a diagnostic? Just to be clear, is the BCM the same as the CCM, just different terminology?
MrWillys, thanks, it may take a few days to get a chance to open up the ECM since it is not garaged at home. Will a VATS delete also require rewiring for the starter?
One thing I am also wondering, would the instrument cluster LED and security light not working indicate an issue with the CCM/BCM? I see that it can be a common issue, so I am thinking I might need to pull out the cluster to check the connector and solder connections.
MrWillys, thanks, it may take a few days to get a chance to open up the ECM since it is not garaged at home. Will a VATS delete also require rewiring for the starter?
One thing I am also wondering, would the instrument cluster LED and security light not working indicate an issue with the CCM/BCM? I see that it can be a common issue, so I am thinking I might need to pull out the cluster to check the connector and solder connections.
Drifting
Joined: May 2013
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From: Reno Nevada
A programmed VATS delete bypass rids the key switch of the resistance check. If there is a fault in the VATS module it may not allow the starter enable relay (uncommon). If this occurs the signal from the module to the relay may be bypassed to rid this also.
I don't think your instrument cluster issue is related to your no start condition.
CCM is for the Passkey that started in 92. Prior it was a VATS module.
I don't think your instrument cluster issue is related to your no start condition.
CCM is for the Passkey that started in 92. Prior it was a VATS module.
Race Director
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From: Anaheim CA
Safety Car
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Maybe not the CCM itself but Module 1 of the diagnostics displays any input faults to the CCM
Read
http://www.corvette-guru.com/uploads...CMCodePull.pdf
if it does it with no jumper you have a problem ; usually memcal ( prom ) related
Advanced
Joined: Jun 2013
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From: Junction City Oregon
Yeah, different terminology but same thing. Central Control Module "CCM", Body Control Module "BCM", same thing located in the dash. My book refers to it as the CCM. Yeah, a little pricey, but, I did all the work myself and saved a bunch from no labor costs. The P.O. bought a CCM from a wrecking yard in California, which is now my spare, and I had no idea if it was good or not. You cannot buy new CCMs so I bucked up and had the original rebuilt. Before rebuilding the original CCM, with it installed in the car, very little of the instrument panel worked. With it rebuilt, everything worked. My spare prom chip was purchased by the P.O. and is a VATS delete chip. With it installed, I kept getting a diagnostic codes for wrong prom. That is why I went back to the original ECM and prom. The cost for reprogramming my CCM including shipping was $290. My new keys were $30. I got a pretty decent deal on the car so throwing a little money at it was no big deal for my situation.
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Drifting
Joined: May 2013
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From: Reno Nevada
A true VATS delete should operate correctly on all levels, and the fan temps can be brought down, custom spark mapping for performance cams, fuel mapping, and enhancing the power enrichment circuit are some of the things good programmers can do. We can even enable highway mode for fuel savings where it runs as lean as 16:1 for 10 second intervals in part throttle cruise situations. The 89 ARAP did this and it works well.
Advanced
Joined: Jun 2013
Posts: 81
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From: Junction City Oregon
I'm sure you are right MrWillys about the VATS delete chip. However, buchacho has a car that had been worked on by the P.O. for some reason he is unaware of. The P.O. owner had a problem, or there would not have been a spare ECM laying in the car. In my case, the previous owner told me he bought a VATS delete chip and new ECM but I did not know how to tell if it was in fact a VATS delete chip, so I went back to the original. I thought I would share my experience with buchacho because his situation is very similar to mine. My CCM was bad, so I had no way to determine the resistance value in it, at least with the knowledge I had at that time. My key would not work with the junkyard CCM, so in effect, I had a car with no ignition keys. buchacho, if your CCM is good, you can bypass the starter enable relay and install a VATS delete prom. Your car should then start once you get a key for your ignition cylinder.
Thread Starter
Heel & Toe
Joined: Jun 2013
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From: California
In what module ; 1, 4 or 9 ?
Maybe not the CCM itself but Module 1 of the diagnostics displays any input faults to the CCM
Read
http://www.corvette-guru.com/uploads...CMCodePull.pdf
Maybe not the CCM itself but Module 1 of the diagnostics displays any input faults to the CCM
Read
http://www.corvette-guru.com/uploads...CMCodePull.pdf
http://www.corvettephotographs.com/c4vettes/codes.htm
I am pretty sure it does it regardless of jumpering the ALDL.
Last edited by buchacho; Jul 23, 2013 at 01:19 PM. Reason: carification
Thread Starter
Heel & Toe
Joined: Jun 2013
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From: California
I have a working "mechanical" key, just the VATS code is unfortunately unknown.
Thread Starter
Heel & Toe
Joined: Jun 2013
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From: California
I just found this, and I am including this as a note for myself and others. It sounds very similar to my issues, but I also am suspicious of the ECM.
http://www.corvetteforums.com/forum/...ead.php?t=9844
http://www.corvetteforums.com/forum/...ead.php?t=9844
The whole story is located under "1991 won't start", but after repainting the car the battery was drained, and somebody left the key in the ignition turned to on, when the charger was hooked it fried the CCM. The car would not crank, the digital dash would not function, but the analog gauges did, and the sercurity light would not come on. I was also gettint code 46 from the ECM.
Race Director
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From: Anaheim CA
Thread Starter
Heel & Toe
Joined: Jun 2013
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From: California
I opened-up the ECM that seems to be working and here is a photo of the chip:
Looks to be an AXCN.
The other ECM did not have a chip.
Looks to be an AXCN.
The other ECM did not have a chip.
Last edited by buchacho; Jul 26, 2013 at 12:56 PM. Reason: photo link updated
Thread Starter
Heel & Toe
Joined: Jun 2013
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From: California
I am in California. Thanks for the offer!
Thread Starter
Heel & Toe
Joined: Jun 2013
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From: California
A couple things I am wondering...
If I got a EPROM with VATs deleted, but the CCM/BCM is not working, will the Vette be able to start? Is it possible to test the functionality of the CCM/BCM through the ECM to get a definitive error code?
I would prefer to keep my EPROM stock, but if it helps get things going quickly, I could opt for getting a spare EPROM with VATS delete. Are there less expensive compatible or knock-off versions of the EPROM (AC Delco PN 16159798) that could be reprogrammed to use as a spare?
Is there an easy way to check if the ECM itself is good?
If I got a EPROM with VATs deleted, but the CCM/BCM is not working, will the Vette be able to start? Is it possible to test the functionality of the CCM/BCM through the ECM to get a definitive error code?
I would prefer to keep my EPROM stock, but if it helps get things going quickly, I could opt for getting a spare EPROM with VATS delete. Are there less expensive compatible or knock-off versions of the EPROM (AC Delco PN 16159798) that could be reprogrammed to use as a spare?
Is there an easy way to check if the ECM itself is good?