04 Suburban Z71 Body Control Module Help

Discussion in 'General Chevy & GM Tech Questions' started by medx421, Feb 28, 2011.

  1. medx421

    medx421 New Member


    I have posted in other Chevy forums. I also have received some good input that has helped me to this point. I am now posting here in hopes of receiving more help.

    This all started with trying to figure out why the only gauges I had lighting up at night were the instrument cluster and the stereo. The climate controls, overhead climate controls, steering wheel buttons, 4wd switch, headlight/dimmer switch, and rear wiper switches never backlit at night since purchasing this vehicle last year. I initially thought it was bulbs on research, however I have since purchased OEM replacements only to have them not work either.

    Last night, I really got a chance to really get into it tonight. I had the luck of having a functional 03 Silverado at my disposal, and later on a friend with a Tech2 scanner. I pulled the headlight control switch w/ dimming wheel out of the 03 and put it into mine. It did not work. Additionally, just to check the quality of the parts that I ordered, I put the HVAC controller into the 03 and it worked fine, backlighting and all. Later when I was able to scan codes, I think I recieved some pretty bad news. It spit out the following codes:

    B2610 - Passenger Compartment Dimming 1 Circuit
    B2615 - Passenger Compartment Dimming 2 Circuit
    B2625 - Display Dimming Pulse Width Modulation (PWM) Output Circuit

    This all seems to stem from the BCM2 module. So, I guess, where do I go from here? Do I need to start looking for a whole new BCM, or is this repairable on another level? We tried clearing the codes only to have them immediately return. The B2610 was the prevalant current code while the 2615 and 2625 were in the history codes. Thoughts?

    Additionally, all fuses are intact and/or have been replaced including the TBC fuses.

    Thank you in advance to anyone who may be able to help. I'm truly losing hair over this.

  2. Taddpole

    Taddpole Member

    I don't know if I can be any help but here are a few things I know about PWM power supplies. Pulse width modulation is a way of changing the voltage applied arross a load by turning it on and off rapidly. So a 12v supply that is turned on and off 50% of the time would average 6v. That would make a 12v lamp run at 1/2 of its brightness. That's a basic explanation. One other thing that I remember about PWM power supplies that I worked with is that they would go into shutdown if there was a short across their outputs. This would protect the power supply. When you cleared the short they would come right back on. So maybe there is a short (bad lamp, crimped wire or wet crusty connector) in your B2610 circuit. I have no idea where that circuit is, maybe a factory wiring diagram may help. If you could isolate that circuit, maybe by pulling the fuse or cutting the power wire to it. Then clear the code and see if it sets again, that would help with your troubleshooting.

    This may not help as I am not real familiar GM bcm's and the bcm could still be bad. Good luck.

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