I have a 2008 H3 with head lights that don't work. Fuse 40 and 41 have been checked, the headlight switch was checked, the multi-function switch was checked, the headlight wire harness was checked, the bulbs were checked, and all were good. There is no power at the headlight fuse. The headlight relay ( #70) was swapped with another, and no change. Fog lamps, turn signals, and DRL all work but no low or high beams. What else can it be? BCM? It appears the prior owner had issues with the sun roof drain tubes as there is surface rust on both sides. I have cleared the front and rear drains and they are clear now. Other than the headlights the truck runs well, without issue. Any help would be greatly appreciated.

 

Without personal verification on my part of your vehicle all I can do is guess.
im going to say check the internals of fuse box for decay, corrosion. Green puss.

 

Take a LOOK at the BCM and its harness for corrosion. BCMs do not like water so any number of electrical problems are possible after moisture intrusion.

 

Thanks Doc Olds....I just checked the BCM and it appears the previous owner had replaced it. There is a white sticker with red writing on it that says "Warranty Void if seal is removed or broken. Recycled Part. Returns not allowed if seal removed or broken 286239." That must be why the front sun roof drains were cleaned out. He must have never found the rear drains because they were solidly plugged. Another thing I just noticed is the odometer is stuck. Probably related to the BCM also. Whats my next move?

 

usually a frozen odometer is that the milage does not match what another module has stored. so if the BCM was replaced with a used one then the milage would reflect the donors and conflict with your actual milage.
as for the headlight you should check if terminal 30 on the relay has power. when the relay closes it should then transfer the power (jump) to terminal 87 of the relay

 

Thanks Bronx...I read that the odometer may not turn until the mileage of the BCM catches up to the actual mileage that is showing on the odometer. Is that accurate? I tested for power at relay 70 terminal 30 and there was nothing. Where do I look next?

 

relay 70 is ground side switching for HI/LO beams. you need to look to see if HDLP relay 75 has power at relay terminal 30.

 

I just checked Relay 75 and both terminal 30 and 85 show power.

 

then the relay is not sending power to relay terminal 27. so either the relay is bad or the relay is not getting the ground trigger from bcm pin A5 to close the relay. or the socket for relay terminal 27 is bad in the fuse box. you can test with a test light with alligator clip on battery positive and probing the relay trigger ground to see if the bcm is sending the ground signal when the headlight switch is turned on. if it lights up then the bcm works and the issue is at the fuse box or relay.

 

Thanks....I will swap the relay tomorrow. If the relay is good, can my existing BCM be reprogrammed? I checked the part number on the current BCM and it is 25816710 . When I checked GM it said the correct part should be 25816709. It seems they may be interchangeable, yet the one I have was originally manufactured for a Chevy Colorado. After doing more research I think the original owner may have had water damage and replaced the original BCM with one he found online and possibly it wasn't reprogrammed with the VIN and mileage from the truck. Would this lead to the headlight issue and the odometer being stuck? To program a BCM is the Tech 2 the only scanner that can do it? I have a Vident i400.