I purchased an 2007 h3 3.7 hummer from an insurance auction. Its a theft recovery. The hummer itself is cherry and looks to be almost garage kept. There's no wires cut or missing and everything is there. According to the carfax, it has right around 90k on it.

When I got it home, the battery was dead and key stuck in ignition. I put a new battery in it and when i turn the key on, the only thing I get on the dash is a check engine light. No other part of the cluster turns on. Also the rear brake lights are stuck on. I replaced the brake light switch with a gm switch and still nothing changed. I also took off the factory terminals and put new ones on since I know that's an issue. This is a non sunroof h3 and I pulled the connectors off the bcm and they look extremely clean. I put my buddies fancy code reader to it and got a u1064 (no connection with bcm) all fuses seem to be good and I did replace the mega 125 fuse to make sure. My gut is leaning towards pcm or bcm but also don't wanna throw money at it if that's not what it is. Any help would be appreciated.

 

Welcome to HF.

Does it have an aftermarket alarm?

The stuck key is GM for dead battery/no power to the ignition.

Check the fuse box to see if the fuse block was pulled and not properly reattached to the Harness Connectors underneath the Fuse Panel in the box. Look for corrosion there as well. Look at this thread for pics and info regarding the Fuse Block and reattaching the Harness Connectors. H3 Alternator R&R from the top. Lots of pictures.

 

Thanks for the reply. Its all stock. stock stereo too. Looks like no aftermarket alarm or anything tapped in anywhere.

I looked at that thread and pulled the fuse box out, inspected and re installed and its doing the same thing and still has rear brake/tail lights stuck on when battery is hooked up.

 

I also just realized that its stuck in park and won't shift out unless I over ride it.

Also the hvac controls and stereo are still not working with Acc Turned on.

Im leaning towards a bad pcm or a bad bcm but would love to confirm before I ship them out for repair.

 

Communication
Grounds
Power

Check your data link and verify your ground, Power and Communication lines are all present and accounted for. Verify with testing not visual. A data probe or light bulb. Ohm all your fuses with continuity test and make sure to visually inspect , plus test grounds next to abs module and behind air box. You'll need to remove each bolt and ispect each and all wires. Also check for continuity from pcm to bcm to data link. There are twisted comm lines that travel from each.
Just dont start parts plucking lol. That is reciep for disaster.

 

Isolate ... Start small... work out from one point.

 

PCM failure on the 07s is NOT common. You already looked at the BCM connections and they were clean right? Track down one thing at a time.

I'd wager there is a high probability that it is in the harness and I would now be looking at the shifter detent switch and its harness and then move to the ignition itself since if it was stolen, they had to tamper with the ignition switch and passlock unless they hauled it away with a tow truck.