BCM/Rear Fuse Box?

STEVE620

MEMBER
2007 GMC ENVOY
4.2L
6 CYL
4WD
AUTOMATIC
119,732 MILES

I replaced the BCM about 3 years ago then started to have the same issues again. There are times when my key fob will not unlock doors and the radio will not go on. I was told that the BCM was failing so I sent it out for repair, it came back, and all was working great for about a year, then same thing again. This time I went to a GM dealer, and they replaced it. Now it's started again. I went back to the dealer and now I'm being told that the rear Relay /Fuse Box that is under rear seat should be replaced. I asked if that was the problem and they said we have to start somewhere. Any suggestions on what I should do?

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

This sounds more like the alternator is overcharging or one of the diodes is bad and it is throwing AC voltage into the system, have you gone through batteries prematurely as well? I would also check the BCM system grounds high resistance can cause the BCM to go out. The BCM only has one ground check out the wiring diagrams in the images below. This guide can help you check the ground, and the second guide will show you how to check for AC voltage.

https://www.2carpros.com/articles/how-to-check-wiring

and

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Images (Click to make bigger)