Intermittent electrical problems 2007 or newer

[CDN MONTANA 2009]

In 2007, GM started using a BCM or body control module. This controls ALL ELECTRICAL components not related to engine operation. So, if you have intermittent electrical problems, you will have to check all components in all circuits to make sure that one component is not feeding back to other circuits. After you have tried all fuses, light bulb sockets, relays, circuit breakers, etc., you may need to replace the BCM. A costly venture!!! It may need to be reprogrammed by the GM dealership. Lower cost to manufacture - higher cost to repair!!!

 

[melsg5]

I understand your point but they dont make cars for the DIY crowd. GM and for that matter all car manufacturers, assumes anybody dealing with these issues will have the appropriate diagnostic tool that can interface with the BCM similar to the scan tool for the ECM. The BCM has it's own set of codes which the tool can read and perform tests with the BCM functions.

 

[CDN MONTANA 2009]

Bcm problems

When hot our signal lights and brake lights fail except the upper brake light. Sometimes power seat dies not work at same time. Is this BCM?

 

[melsg5]

There is no way of telling without a diagnostic scanner capable of checking the BCM. Did you try a voltmeter or test light to see if power is going to the socket when you have the problem. There are also junction points that can fail and require a wiring diagram.

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[bobcardone]

Possible fix

There is a huge wiring bundle that runs in a channel under the passenger carpet.
Pull the trim panel off and peel the carpet back, there it is.
Any water leakage will pool here, and there are at least five soldered junctions (maybe more) that will corrode and cause all sorts of freaky electrical problems.
I had this issue, and just spent an afternoon finding and repairing bad connections in this area.
Solder and heat shrink any suspicious junctions.
On my Montana, this fixed the remote locks, rear window motors, side door locking and remote mirrors.
Crappy GM engineering, but easy to get to and fix.