BCM or passive restraint system 94 LT1
Thread Starter
6th Gear
Joined: Sep 2013
Posts: 6
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BCM or passive restraint system 94 LT1
Long time reader, first time asking for help! Haven't drove my 94 Vette all summer, (LT1 6 speed) been through 3 used BCM units, can't seem to get any to link up, thinking about just having mine rebuilt because GM doesn't even sell them. My Vette will start with the current BCM, but if I drive it down the road and shut it off, many times it wont start, But, wait for 30 minutes and then it starts. Corvette shop told me my BCM was going bad and wanted $1200, I thought..Noway!! me and my buddy that knows car pretty well can do this! I have bought 3 used ones that appear to be the same as mine, won't link up! Nothing happens, except I can read the milage of the BCM I am trying to install, so I put the old one back in, fires up and runs great!!....Except I keep getting stuck places! I heard there was a forum where others have had this same problem which took years to figure out???? My buddy now thinks its the passive restraint system??? Just wondering if anyone has had this same problem, or could head me it the right direction. Appreciate any insight, I have seen so many problems solved on this site!
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
been through 3 used BCM units, can't seem to get any to link up, thinking about just having mine rebuilt because GM doesn't even sell them. My Vette will start with the current BCM, but if I drive it down the road and shut it off, many times it wont start, But, wait for 30 minutes and then it starts.
Spark or fuel.
Not likely the problem is the BCM (Body Control Module)
also called the CCM (Central Control Module).
When you purchase a used BCM/CCM you need to know
what key pellet resistance value it was programmed for.
When the key pellet is read properly by the CCM when you
turn the ignition switch to On, the Security light in the dash
cluster should go Off. If it stays on, that indicates the
key pellet resistance doesn't match what the CCM was
programmed for and the starter will not engage.
To find the correct resistance value is found by trial and error.
Last edited by Hooked on Vettes; Sep 19, 2013 at 01:00 AM.
Thread Starter
6th Gear
Joined: Sep 2013
Posts: 6
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that all makes perfect sense, because the security light stayed on, I am beginning to believe that I got bad info from my Corvette shop! I remember that when he tested both of my keys (he had this little tester box that he put the key into), the pellet in them both were not very good, but he said they both worked, maybe put old BCM back in the car, and have a new key made and see if that solves the problem? Any other ideas? Oh thanks for the quick response!
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 42
From: Baltimore, MD USA
What do you mean won't restart?
Engine won't crank?
Security light stays on?
If the Security light stays on that indicates the key pellet wasn't
read properly and a lock out period of around 4 minutes takes place. During this time if you try to start the car again the
time out period starts again.
If the key pellet is good most likely the ignition key cylinder wires
are bad. Every time you turn the ignition key cylinder the wires
twist and eventually break.
Most people take a resistor and place it across the two wires
going to the CCM that normally connect to the key cylinder.
Short either pin 4 or 5 to pin 12 on the diagnostic connector above
the drivers right knee. Turn the ignition On. Look at the dash cluster
LCD and see if any codes are set.
Module 1 is for the CCM.
Module 4 is for the PCM.
If any codes are set note what they are. Clear any codes, by disconnecting the negative battery terminal for a couple of seconds then reconnect.
Engine won't crank?
Security light stays on?
If the Security light stays on that indicates the key pellet wasn't
read properly and a lock out period of around 4 minutes takes place. During this time if you try to start the car again the
time out period starts again.
If the key pellet is good most likely the ignition key cylinder wires
are bad. Every time you turn the ignition key cylinder the wires
twist and eventually break.
Most people take a resistor and place it across the two wires
going to the CCM that normally connect to the key cylinder.
Short either pin 4 or 5 to pin 12 on the diagnostic connector above
the drivers right knee. Turn the ignition On. Look at the dash cluster
LCD and see if any codes are set.
Module 1 is for the CCM.
Module 4 is for the PCM.
If any codes are set note what they are. Clear any codes, by disconnecting the negative battery terminal for a couple of seconds then reconnect.
Last edited by Hooked on Vettes; Sep 19, 2013 at 02:28 PM.
Thread Starter
6th Gear
Joined: Sep 2013
Posts: 6
Likes: 0
Sorry it took so long to get back, drove my Vette last night, when I got home, it won't start, when I say it won't start, it doesn't turn over, clicks like everything turns on, lights light up but nothing, some of the light do stay on, the
Battery light, Service light and the airbag light stay on only. Tried waiting for 4-5 minutes and tried to start it again, still nothing, 20 minutes later, fired right up like nothing was wrong, it will always start if it has been sitting. Not so sure I can run the test that you mentioned, I have a buddy of mine that can. Wondering if it is the chip in the key, or the key cylinder. Thanks for your help, I will wait for your response, then I will probably buy a new key, and Key cylinder
Battery light, Service light and the airbag light stay on only. Tried waiting for 4-5 minutes and tried to start it again, still nothing, 20 minutes later, fired right up like nothing was wrong, it will always start if it has been sitting. Not so sure I can run the test that you mentioned, I have a buddy of mine that can. Wondering if it is the chip in the key, or the key cylinder. Thanks for your help, I will wait for your response, then I will probably buy a new key, and Key cylinder
Drifting
Joined: Feb 2013
Posts: 1,465
Likes: 12
Sorry it took so long to get back, drove my Vette last night, when I got home, it won't start, when I say it won't start, it doesn't turn over, clicks like everything turns on, lights light up but nothing, some of the light do stay on, the
Battery light, Service light and the airbag light stay on only. Tried waiting for 4-5 minutes and tried to start it again, still nothing, 20 minutes later, fired right up like nothing was wrong, it will always start if it has been sitting. Not so sure I can run the test that you mentioned, I have a buddy of mine that can. Wondering if it is the chip in the key, or the key cylinder. Thanks for your help, I will wait for your response, then I will probably buy a new key, and Key cylinder
Battery light, Service light and the airbag light stay on only. Tried waiting for 4-5 minutes and tried to start it again, still nothing, 20 minutes later, fired right up like nothing was wrong, it will always start if it has been sitting. Not so sure I can run the test that you mentioned, I have a buddy of mine that can. Wondering if it is the chip in the key, or the key cylinder. Thanks for your help, I will wait for your response, then I will probably buy a new key, and Key cylinder
My wires for the vats went out/broke and i could not start the car at all. I personally dont think this is your issue but for the 5 bucks its worth a try. good luck to ya.
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Thread Starter
6th Gear
Joined: Sep 2013
Posts: 6
Likes: 0
No, it either starts or it doesn't, I just drove it to my office, turned it off and then started it, fired right back up twice and the 3rd time it didn't. Turn the key, no battery or starter noise at all, lights come on and then go off except for the Battery light, Service light and the Airbag light stay on. But I let it sit for 20 minutes and then it will start. It always starts after sitting!! But only 50% chance of it starting after running, wether it is running for 1 minute with no time to warm up or an hour after its hot.
Le Mans Master
Joined: Sep 2013
Posts: 6,192
Likes: 750
From: near the thumb in the mitten
Keys almost never go bad. Dealer has a tool which reads keys and analyzes cylinder. Tool hooks up in key circuit. key code with key in cylinder should match code when key is inserted in slot in tool. When key is turned code should not flicker. It is possible cylinder is on it's way out. If it passes test - key /cylinder not the cause. Starter enable relay is another common cause. Other possible poor battery connections, poor grounds, clutch switch adjustment, starter.
Thread Starter
6th Gear
Joined: Sep 2013
Posts: 6
Likes: 0
OK, thank you for all of your quick responses, My vette started up after work and I ran it hard on the way home, raced an SUV and a Mustang, LOL!!! Why do people always want to race a Corvette when they know they can't even come close??? Anyway, got it home and it won't start, checked the lights that stayed on, and the security light does stay on, as the air bag light flashes and goes off, but waited 20 minutes and it fires up…..so OK I will take the info I have gathered here to a couple places and see what I can come up with. I appreciate your help, Thank You