HI, AND THANKS FOR ANY INPUT IN ADVANCE. MY A. S. LIGHT CAME ON I TOOK TO THE DEALER 3000 DOLLARS LATER I PICKED IT UP, DROVE 2 MILES, LIGHT COMES ON AGAIN. I TOOK IT RIGHT BACK AND THEY SAID IT HAD 4 UCODE ERRORS (THAT WASN'T THERE WHEN I LEFT. THEY SAID BRING IT BACK IN 4 DAYS BECAUSE OF THE HOLIDAY. TOOK BACK TODAY, 14 MORE UCODE ERRORS (DIFFERENT ONES, SOME THE SAME) THEY ALSO SAID THEY FORGOT TO MENTION MY TRUCK STARTED BY ITSELF WHILE THERE LAST TIME THEY WERE WORKING ON IT. NOW THEY WONT LOOK AT MY LIGHT ISSUE UNTIL I GET MY REMOTE START REMOVED THEY CLAIM THAT'S WHAT IS CAUSING ALL THESE UCODE ERRORS. i HAVE A 2003 H2. THANKS AGAIN!

 

Sorry, i forgot to mention the dealer replaced my air suspension compressor

 

Certain aftermarket devices use the communications bus to do things since its much easier for wiring. The side affect is if the aftermarket devices communications controller is poorly implemented it can cause lots of unnecessary messages, noise, chatter, etc on the communications bus which can freak other controllers out.

A good example are aftermarket stereo adapters. I have an aftermarket stereo in mine but I chose to keep the factory Bose lux amp and also wanted to use the factory steering wheel controls. For this to work I used a Metra (very well known aftermarket audio adapters) interface harness. This Metra harness sends serial communications on the factory wiring to control the factory amplifier and the steering wheel controls. It works great.

I also have a Tech2 and two different tuners (full EFI Live and a Diablosport Intune). As an example - I had the Intune connected to the OBD port to install a tune and it would fail and go into recovery mode and just freak out. So I connected the GM Tech2 and figured okay I'll update the ECU to the most current version from GM. I just nearly bricked the ECU. The Tech2 did its thing using the SPS (Service Programming System) and updated a couple of other modules first like the DDM, then on the ECU it got about 50% of the way through writing and gave an error. The truck was dead. Dash would light up and that was it. No start, no fans, windows etc would not work, nothing. Looked online and everything said to disconnect anything aftermarket that might communicate on the factory bus like stereos, alarms, remote starts, etc that might try to actuate locks, ignition, amplifiers, etc. Turns out it was the stereo adapter freaking things out. Pulled the fuse for it and luckily the ECU write failure did get far enough to write the boot loader. So it was able to retry and fully reprogram things.

Also with the fuse for the stereo adpater out, the Intune and the EFI Live (the one I primarily use) both can read/write, etc just fine. So the point is - the dealer has no idea what aftermarket device could be doing weird things on the bus and communicating. Them saying it remote started while working on it says (I'm suspect if it really did - they could just be saying that) they suspect something could be interfering with the Tech2 communicating properly with the modules. If it did actually try to remote start without the remote requesting it to while being serviced, that is dangerous.

On other possible consideration. The 2003 models air ride used an older style compressor which is no longer available. If replaced they get replaced with the newer dual pump style one. If a dealer (or someone with a Tech2) attempts to update the air ride computer module software on an older model with the newer compressor it will brick the module. See here https://gm.oemdtc.com/4387/rear-air-...2005-hummer-h2

 

Thanks MixManSC. I just got off the phone with the dealership and he said they did no software updates. Only put the compressor in and replaced the sensors and the wire harnesses.

 

JUST A UPDATE.I had the remote start removed on a FRIDAY LEFT MY TRUCK AT HOME CAME BACK ON Sunday and my rear end was sitting low when i started it every light on my dash was lite up and no air,widows would not work, locks would not work and the radio .I took it back to the guys who unhooked my remote start and after looking at it for a few hours they unplugged the module to the compressor and everything started to work again.So,i took it back to the dealer they agreed there was no communication to the compressor.So, i got it back today with a new compressor and now my truck won't start without a jump and the dealer claims that they told me last time it would not start and that they told me that .I called their bluff they made me remove my remote start cause they claimed it started by itself the last time it was there. How was that if my battery died on them.I am taking it back to my electric guy tomorrow to test the charging system I'll keep updating in case anyone has luck like mine. but the air suspension light isn't on anymore.

 

Dang! What an ordeal to go through to figure this out. Best of luck with it. Maybe just a few things compounded together to make troubleshooting much more complicated.