Changed BCM need help!!!
Thread Starter
Instructor
Joined: Jul 2008
Posts: 232
Likes: 0
From: Bristol VA
Changed BCM need help!!!
Ok I have a 99 A4 coupe and my BCM went out so I got another off a forum member that came out of a 00 A4 coupe with the same options as my car everything works but I can't get the car to crank over and I checked the battery and its good.
So does anyone know if theres somthing I have to do or what the problem might be?
So does anyone know if theres somthing I have to do or what the problem might be?
Tech Contributor
Joined: Jan 2007
Posts: 19,363
Likes: 1,128
From: Dyer, IN
Did you do the BCM-PCM relearn procedure????? If not it ain't going to run.. From a post I copied a ways back:
BCM/PCM RELEARN PROCEDURE
You will need to conduct the PCM/BCM relearn process. This matches their handshake ID's and allows them to talk to each other.
Do this before you worry about VATS issues:
1. Turn on the key for 11 minutes.
2 Turn off the key for 30 seconds.
3. Repeat 1&2 two more times.
4. Turn on the key for 30 seconds.
The car should start and run with the new BCM
BCM/PCM RELEARN PROCEDURE
You will need to conduct the PCM/BCM relearn process. This matches their handshake ID's and allows them to talk to each other.
Do this before you worry about VATS issues:
1. Turn on the key for 11 minutes.
2 Turn off the key for 30 seconds.
3. Repeat 1&2 two more times.
4. Turn on the key for 30 seconds.
The car should start and run with the new BCM
Thread Starter
Instructor
Joined: Jul 2008
Posts: 232
Likes: 0
From: Bristol VA
Did you do the BCM-PCM relearn procedure????? If not it ain't going to run.. From a post I copied a ways back:
BCM/PCM RELEARN PROCEDURE
You will need to conduct the PCM/BCM relearn process. This matches their handshake ID's and allows them to talk to each other.
Do this before you worry about VATS issues:
1. Turn on the key for 11 minutes.
2 Turn off the key for 30 seconds.
3. Repeat 1&2 two more times.
4. Turn on the key for 30 seconds.
The car should start and run with the new BCM
BCM/PCM RELEARN PROCEDURE
You will need to conduct the PCM/BCM relearn process. This matches their handshake ID's and allows them to talk to each other.
Do this before you worry about VATS issues:
1. Turn on the key for 11 minutes.
2 Turn off the key for 30 seconds.
3. Repeat 1&2 two more times.
4. Turn on the key for 30 seconds.
The car should start and run with the new BCM
Drifting
Joined: Feb 2008
Posts: 1,596
Likes: 67
From: Bahama North Carolina
Make sure you have a full charge on your battery before you start this procedure or you may run out of juice before it completes the cycles.
1. Turn on the key for 11 minutes.
2 Turn off the key for 30 seconds.
3. Repeat 1&2 two more times.
4. Turn on the key for 30 seconds.
1. Turn on the key for 11 minutes.
2 Turn off the key for 30 seconds.
3. Repeat 1&2 two more times.
4. Turn on the key for 30 seconds.
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
Just the FYI for the OP, the BCM and PCM exchange a hidden password between them therefore preventing someone from stealing your car by changing out the BCM and using the wrong key. If the password exchanged between them doesn't match on both ends, the starter will not function. The relearn will take care of this although it will not match up RPO codes. If you vehicle is identical to the one the BCM came out of, all should work but if not, you'll need either a Tech 2 or a trip to the dealer.
Tech Contributor
Joined: Jan 2007
Posts: 19,363
Likes: 1,128
From: Dyer, IN
Just the FYI for the OP, the BCM and PCM exchange a hidden password between them therefore preventing someone from stealing your car by changing out the BCM and using the wrong key. If the password exchanged between them doesn't match on both ends, the starter will not function.
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
hmmm....I thought I read that area of the manual carefully on the '99 that I gave away to my son. Since I'm getting it back shortly and the manuals, I'll re-check what I thought I read. For now, I'll assume I'm wrong and you are correct. Either way, if things aren't satisfied, it won't start!
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