Hello,
I have a bit of an issue with our Hummer.

2006 Hummer H2 - 90,000 miles. Wife went in the wet ditch at low speed and vehicle ended up having water in cab (at 45 degree angle). She went in parallel with the road so water never made it to the center or passenger side of vehicle.

I ended up taking out the interior including doors and dehumidified the vehicle for a week, took every electrical component apart, sprayed with contact cleaner, blew out with high pressure air and applied a light coat of dielectric spray grease to try to hinder any oxidation. ECM was underwater so I bought a new one and had programmed to vin. Took out every fuse and replaced every relay and did the same contact cleaner/grease things. I even took the engine bay fuse block apart in the same manner.

Vehicle starts and runs perfect (engine and tranny stayed above water due to steep angle of ditch).

Here is my issue:
When the key is in the on position, gauges and drivers windows/door controler work. When I actually start the vehicle, the 4 gauges (oil, battery, fuel, temp) stop working. Drivers window/door controls stop working, 4wd selector stop working and the ABS, Airbag, battery lights come on.

When I turn the vehicle off then back to the on position (not started), the gauges and windows/locks/mirror work as normal.

Any ideas of a correlation of those issues and what would cause this?

I sure do appreciate any suggestions

 

First thing you need to do is get a full function scan tool and scan every module in truck, see if any are not communicating while engine is running. Then try with engine off key on. compare the two and that will narrow down your search. I would suspect something is going offline due to poor connection once engine is running

 

Humtech- Thanks for the input. I will need to try and gain access to a good scanner to try and narrow this down.

 

Update: I was able to get my hands on a very nice scanner that I was able to run a scan and clear all codes other than C0055 (Right Rear wheel speed sensor circuit) which I assume just needs to be replaced. All was going well and I was doing some drive testing (scanner has live data) while my wife was driving and then I started to lose communication through the obd and the gauges and windows would stop working. All the while the truck was driving and never skipped a beat.

This makes me think that I might have a power or ground issue with the BCM.

Does anyone have information for the power and ground path for the BCM? I think that is the path I should follow. If I determine that I do have proper ground and power to the bcm then I can only assume the bcm will need to be replaced.

 

Resolved:
I know people come here for help then never come back after they solve the problem. I was not able to fix the problem myself. I ended up bringing it to a shop and they determined that the ABS module (on the frame on the drivers side under the truck) was damaged and taking down the bus system. They replaced with a used part and everything is now perfect. With the testing, used part and installation labor the cost was about $800.00.

 

Thanks for getting back to us. Those dang ABS components seem to cause the weirdest unrelated (seemingly) problems. Glad you got it sorted.

 

Sounds like you found a competent shop that repaired it right the first time. You should buy them some doughnuts.