I just bought my 2007 H3X from a private owner. I noticed the "service charging system" message before I bought it, thinking it was just a code that needed cleared out by the dealer or a combination of brake pedal and key turns. The previous owner when asked said that they did not have the message until they replaced a dead battery. I went to Auto Zone and the Kid said I need a new alternator due t it charging over 15 volts. So I then went for a second opinion at Advanced Auto. He ran a more in-depth scan on the battery having me run it at 3000rpm and turning on all of the things I could to put a load on the system. He came up with nothing wrong, alt, batt and starter were all fine. It did say the batt was bad due to him putting my 650 CCA battery in at 850 CCA. So I went to a dealer ship (Toyota where my buddy works) and had them run the scanner and clear the code. The code was cleared and came right back and he came back with a B1390 code (Device Voltage Reference Input)
Now one other thing I noticed was that this H3 has been chipped. It has a Stage 1 Jet performance power control module installed.
Any ideas on what could be wrong??

 

Even though no one had an answer i found the issue with my charging system. I bought a repair guide on eBay (downloadable) for $6.50. It had everything I needed to narrow down the problem. The issue was a plug for the wiring harness between the battery box and the fuse box. The old battery must have leaked onto it and corroded the orange wire connection that went to the GBCM. I found this by checking the connectivity with the ohm meter between the GBCM and the #32 fuse. Then I traced the wire to the connector in front of the battery box.

Auto stores said Replace the $200 alt. All I had to do was spend $6.50 on a very helpful service manual….

 

Good info. Thanks

 

Had the same issue. If you pull the chip it will go away guaranteed. You wont notice a HP difference, that chip is junk. My 2 cents for what is worth.

 

I tried that already. I did notice a drop in the HP not much but a little. And it shifted smoother with the chip. But it still had the issue with the service charging system. The chip is a stage 2 not 1 like I stated in the 1st post. But like I said the wire was the issue.

 

Tanks for da tip...
Chris

 

TheEdge ... thanks for that info. As I 1st time Hummer owner anything I learn in repair I put in my own database that I am building.

What was the title you searched for on eBay for that $6.50 repair download, I'd like to buy that same one for my 2006 H3.

 

2006-2009 Hummer H3 Service Repair Manual via DOWNLOAD (181000124869)

This is what i bought on E-Bay for a manual.