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Would a bad BCM cause these Symptoms, or other cause? ('93 40th Anniv Corvette Coupe)

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Would a bad BCM cause these Symptoms, or other cause? ('93 40th Anniv Corvette Coupe)

 
Old 03-07-2019, 10:56 PM
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ROCKETmn
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Default Would a bad BCM cause these Symptoms, or other cause? ('93 40th Anniv Corvette Coupe)

I'm having the following very challenging problem:
Symptoms: Corvette starts up immediately and the engine runs perfectly, BUT after exactly 15 minutes the interior lights flicker and keep flickering, although the car continues to run perfectly. We don't know how long it would run once flickering starts since we didnít explore that, but it does not cut out. Originally the security alarm sounded too, but we disconnected it. If the car sits and cools, itíll start up again and will repeat the same sequence as described above. To start the car right away, we need to detach the battery for a bit, and upon reconnecting the battery, the BCM is "reset", and it'll start up again and will repeat the same sequence as described above.

Questions:
1. Is the BCM the problem and is it fixable? Will rebuilding the BCM fix it? (A Corvette Dealer in our area said that it's the BCM and that it's not fixable. - Hard to believe.)
2. If the BCM in not the problem (i.e. found not to need rebuilding), what could cause the above symptoms? Could it be a short in the harness, and if so how could that be tested and fixed?

Thank you!
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Old 03-08-2019, 08:26 AM
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Kevova
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CCM would be proper term. Factory Manuals? CCM will store fault codes. Are there CCM and/or ECM codes? Alarm added accessory? If so it should be completely removed.
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Old 03-08-2019, 09:10 AM
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VETTLIFE
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Sounds like door wiring is rattling and shorting to ground when the car hits a specific RPM during idle. The door wiring also carries a alarm arm/disarm signal for the door lock.

If you've confirmed this isn't the problem I would check vats operation. If memory serves right the interior lights flash when there is a problem with vats code mismatch. If this is the case, diagnostic codes will reflect this. When you unplug the battery your likely resetting vats. Another way to verify if it is vats is the next time the car won't start simply take the key out and wait at least 6 minutes without touching the ignition then try it again. If the cars starts then you know vats is the problem.

Otherwise it is likely a dirty, poor connection to the CCM. I would then proceed to pull it and give it the iso clean treatment checking and cleaning terminals as you go.

Last edited by VETTLIFE; 03-08-2019 at 09:15 AM.
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Old 03-08-2019, 09:24 AM
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I have a good, spare, working 92-93 BCM/CCM available if you decide to go this route. VATs Key #11. Would need key number and VIN reprogramming with your dealer's Tech 1.

Last edited by old_vette; 03-08-2019 at 09:26 AM.
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Old 03-11-2019, 11:12 AM
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anesthes
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Originally Posted by old_vette View Post
I have a good, spare, working 92-93 BCM/CCM available if you decide to go this route. VATs Key #11. Would need key number and VIN reprogramming with your dealer's Tech 1.
You can re-program a used CCM ?

-- Joe
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Old 03-11-2019, 11:23 AM
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^Yes. "You" (you and I) can't, but it can be done.
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Old 03-11-2019, 11:53 AM
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I can't, but the dealer can. Way beyond my understanding.
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Old 03-11-2019, 01:16 PM
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anesthes
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Originally Posted by Tom400CFI View Post
^Yes. "You" (you and I) can't, but it can be done.
With a tech 1 or tech 2 ? I see them all the time on ebay. I almost bought one a few times, but I was under the impression after 100 miles or so the CCM is "locked" and CANNOT be reprogrammed ?

-- Joe
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Old 03-11-2019, 01:38 PM
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Tom400CFI
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IDK about using a Tech 1 and what it can or cannot do, but "I know a guy" who can reprogram a used one regardless of it's previous usage. I can post his info, if you'd like....
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Old 03-11-2019, 02:41 PM
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Originally Posted by Tom400CFI View Post
IDK about using a Tech 1 and what it can or cannot do, but "I know a guy" who can reprogram a used one regardless of it's previous usage. I can post his info, if you'd like....
That would be great, I'd love to ask him what he's using.

When I tried to have one programmed back in 2006/2007 the dealer told me it wasn't possible.

-- Joe
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Old 03-11-2019, 02:59 PM
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Ken Anderson
[email protected]
kandbcorvetteproducts.com

770-777-1031
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Old 03-11-2019, 06:51 PM
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Originally Posted by anesthes View Post
That would be great, I'd love to ask him what he's using.

When I tried to have one programmed back in 2006/2007 the dealer told me it wasn't possible.

-- Joe
I would get a 2nd opinion! Sounds like he was too busy with not much revenue to be generated, given the PITA it is, not to mention the need for a knowledgeable shop tech on board. Perhaps he didn't have his flat rate manual handy, or didn't know where to look.

Jack
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Old 03-12-2019, 06:17 AM
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Did you pull any codes? The ECM and CCM each report separate codes and can be found by jumping the ALDL connected A and G pins together with a piece of wire and reading the codes on the LCD display on the cluster. The connector can be found under the dash. (Note, most wiring diagrams show it upside down).

This sounds like a VAT problem to me, it's extremely rare that CCM's fail on these cars. I wouldn't suspect it's the issue.

In very rare cases if the CCM is at fault they normally get repaired instead of replaced. There are a number of places that can do this.
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Old 03-12-2019, 07:43 AM
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Originally Posted by ROCKETmn View Post
I'm having the following very challenging problem:
Symptoms: Corvette starts up immediately and the engine runs perfectly, BUT after exactly 15 minutes the interior lights flicker and keep flickering, although the car continues to run perfectly. We don't know how long it would run once flickering starts since we didn’t explore that, but it does not cut out. Originally the security alarm sounded too, but we disconnected it. If the car sits and cools, it’ll start up again and will repeat the same sequence as described above. To start the car right away, we need to detach the battery for a bit, and upon reconnecting the battery, the BCM is "reset", and it'll start up again and will repeat the same sequence as described above.
It's possible, but unfortunately I would probably recommend getting into the dash and checking connections first...I suspect something is heating up and bending away for a good contact. As others suggest check for codes, but there is no easy way to troubleshoot electrical problems.

What you could try doing is buying a fuse circuit tester and seeing if there is a change in amps when the problem starts, of course that's a lot of trial and error type work, but the checker is cheap enough.

Also rather then disconnecting the battery, pull the fuse to the CCM instead to see if that lets the car start up again.
https://www.harborfreight.com/30-amp...ter-67724.html

Of course could just be a bad fuse that is heating up and breaking contact, double check all fuses.

Last edited by bac22; 03-12-2019 at 07:44 AM.
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Old 03-12-2019, 04:36 PM
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Thank you for the clarification on CCM.
I'll ask the mechanic for any codes and reply again.
The Vette is all stock, as purchased, and thus so is the alarm ("Theft Prevention System").
Thank you again!
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Old 03-12-2019, 05:54 PM
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Thank you ALL for these suggestions, all of which I'll discuss with my long-time mechanic that has been working this problem.
I'd like to focus on "more basic" suggestions first (e.g. checking all connections, check fuses, et al) and getting the diagnostic codes from the ECM and CCM (which I'll send out), before considering a rebuild of my current CCM.
Question: Are all CCM rebuilders created equal? Are there Vette CCM rebuilding specialists that would be better than those that rebuild control modules of ANY CAR ?
If the above basic tasks don/t fix the problem, and I need to pursue the rebuild, I'd like to know of a reliable Rebuilderthat can ensure that they can do the rebuild, or at least they don't charge if no rebuild is necessary. My mechanic had also heard that the CCM locks after 100 miles, thus cannot be rebuilt, so this will
I'll have my mechanic contact the kandbcorvetteproducts.com referral, but also Zip-Corvette.com, who said that there wouldn't be a rebuild charge if the CCM didn't need rebuilding, and they "said" that they "rebuild more CCMs than anyone". : - )
I also found CorvetteCentral.com, but I couldn't speak with a knowledgeable person about the exact symptoms.
PLEASE continue to send additional thoughts on reliable CCM rebuilders, and I'll let you know the results of our next steps.
Thank you all again!
Don

.
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Old 03-12-2019, 06:34 PM
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(Note: Resending this reply since I never saw my 1st reply post of this message in my posts. Sorry for any duplication.)

Thank you ALL for your suggestions! I will give all of them to my long-time mechanic who has been working this problem. We'll first do the "basic" items (e.g. check all connections, check fuses, et al) and will pull the codes from the CCM and the ECM (which I'll send out to you all when I get them), before considering the CCM rebuild.
If the above items do not fix the problem, I'll then consider the CCM Rebuild, but would like a rebuilder that can ensure that they can rebuild the CCM, despite the belief that the CCM locks up after 100 hours. I'll have my mechanic contact and consider the "kandbcorvetteproducts.com" referral (thank you), and also another I had considered, Zip-Corvette.com, who said that there wouldn't be a rebuild charge if the CCM didn't need rebuilding, and they "said" that they "rebuild more CCMs than anyone". : - )
PLEASE share more suggestions on exceptional and reliable CCM Rebuilders, and valication of the ability (or inability) to rebuild a CCM that has been "locked up" after 100 mile (or so) preventing a rebuild.
Thank you all again for your suggestions!
I'll let you know of our progress!
Don
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Old 03-13-2019, 03:10 PM
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J.Abbott
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Don,
I am not sure how many times I have talked to you, but you are not giving everyone all the details on this car. Did you try the ground strap? I didn't think about door wiring but that is a good one to pursue. I also did not say it would not cost anything if the CCM was not the issue, you mis interpreted that. If we do the CCM service, it is a rebuild and new software, that we will charge for. Your issue is not the CCM though, at least 95% sure on this. Check your grounds and then check your door pin connectors these do go into the CCM but the fact that the car starts running bad at the same time makes me believe it is not the CCM causing this. The CCM does not control anything with the engine other than starter enable and injector enable. In that this car was put together I am still going with it is a ground issue.
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