I recently purchased my H3 only to find it had several issues that turned out to be common and simple to fix. I've been able to rectify all my faults because of the generosity of this community. So I'm going to share my experience and hopefully post something useful to help others.

My H3 had all 4 drain tubes blocked for the sunroof. When I lifted the carpet the floor was full of water and soaked all the way through. I wouldn't have known until I coincidently looked under the carpet solving an aftermarket wiring system. The water was so bad I had to remove all the inside and have the carpet professionally steam cleaned and hung in a dehumidifying room for 5 days. There were small rust bubbles coming through the paint too

I've since drilled out the grommets of the drain tubes where the (+) shape is and no more leaking.

Driving it home for the first time it was raining. Water was occasionally pouring on my head and after a few hours and I got the DTC: ABS Fault Traction Control Failure Service Stab System. I purchased the BlueDriver scan tool as it can access all the Hummer's codes. Best money i've spent as it told me directly what was causing the MIL. I got C0186 or C0196 depending on when I scanned it. This tech guide has all the ABS answers: http://schwarttzy.com/wp-content/upl...ake-System.pdf

DTC C0186 or C0196 Lateral Accelerometer/Yaw Rate Circuit

I ordered a new Yaw sensor off Amazon plugged it in and my problem was solved immediately.

Water had obviously damaged the Yaw sensor as its located under the carpet of the front seat.

Heres a video of my experience. Hope it helps you solve your DTC too
https://www.youtube.com/watch?v=v89MyNDVkxs

 

Sorry to hear of your H3 issues. It's amazing how many things can go wrong once the drain tubes get clogged.
Due in part to this forum I inspect and clean my drain tubes yearly, and avoid parking under trees (epecially pine).