I had the EXACT same issue with my 2007 H3, word-for-word. Brake lights would not "light up" when brake was pressed and turn signals did not blink. I replaced both bulbs, replaced fuse (which kept blowing) passenger tail light stayed on when truck was turned off (key out of ignition) until the fuse would blow...

I took it to an Auto/Electric shop which could not find the problem.

FINALLY...
Took it to the Dealer. They found that due to some broken wires...the BCM (Body Control Module) went bad...

$785.00 plus tax to replace the BCM and program it.

Problems fixed tho.

 

I had the EXACT same issue with my 2007 H3, word-for-word. Brake lights would not "light up" when brake was pressed and turn signals did not blink. I replaced both bulbs, replaced fuse (which kept blowing) passenger tail light stayed on when truck was turned off (key out of ignition) until the fuse would blow...

I took it to an Auto/Electric shop which could not find the problem.

FINALLY...
Took it to the Dealer. They found that due to some broken wires...the BCM (Body Control Module) went bad...

$785.00 plus tax to replace the BCM and program it.

Problems fixed.

 

So my 09 H3 now has 100thou klicks on it (the magic mileage for issues)
first asstupid simple and easy as it sounds CHECK AND CLEAN YOUR BATTERY TERMINALS!!!
My H3 started to have popping through the radio every time I hit the brakes, it became worse and worse (not a huge issue but annoying)
then my next drive I noticed my lights dimming very slightly every once in a while so incremental I dismissed it to bumps.
drove like this with these issues intermittent for about a month.
i started doing some reading and thought it was under the dash grounds loose.
well what I read was for earlier hummers and found no under dash grounds anywhere near the kick panel and I’ve babied my h3 so everything else looked tidy and new.
drove again and this time when I started the truck all of my temp ***** flashed until I put it in drive...wierd...left home and heard the radio hum...grrr
Now on the freeway suddenly my dials all dove and the door locks went on and off as if possessed!
Ok now it’s seriouse as I had my wife and baby with me.
Im a car guy but this was new age electrical so discussed with my wife and if after tinkering the next day if I couldn’t figure it out we would go to the stealership mechs...they should know and have the correct equipment right?
that night I did more reading and learned of the BCM!
other guys had the same issues then replaced it! But apparently these stupid computer things need to be reprogrammed after install and the dealers didn’t do that so now same problems and more for these poor guys...I’m cheap and hate dealers so I kept reading but kept the BCM in mind.
Then I read one saving line in a post...it said “Usually if there are multiple strange electrical issues seeming to all be different it is more than likely a ground.
That night I popped the hood and found on my 09 what appears to be ground posts on the middle top of each inner fender with multiple grounds to them.
They looked fine.
I then hoped like buying a can of “just pour in engine fix” that the battery terminals would have obvious corrosion
....to my eye there was maybe a film (no white gobs or anything) and a slight green corrosion tint.
So I crossed my fingers thinking; no not enough corrosion to effect it (even though I read that these new vehicles were super sensitive to power fluctuations or minuscule voltage)
changes)
-So I soaked the leads in vinegar over night,
-dremmeled and sanded the posts and connections on the battery leads,
-scrubbed the ground posts on the fenders with vinegar and baking soda
and gave them a snugging 1/8 of a ratchet turn.
and let it all dry over night.
(the battery tested to be fine)
The next morning like a bottle of miracle engine fix....ALL OF THE ISSUES HAD GONE AWAY!!!
I FIXED THE STUPID THING FOR FREE WITH NO STEALERSHIP!!!
so the lesson I learned was even as a car guy thinking “No it must be more complicated!”
start with the easiest cheapest thing first even though it seems imasculating to have to say “It was just dirty battery terminals.”
dealerships will guess and happily replace everything possibly causing more issues like all of those poor guys with the same symptoms that replaced BCMs alternators and everything else that may have had the same issues as me.
(ps possible that the slight tightening of the fender grounds could have done it too but I doubt it...but hey it’s free and easy to try.)
This was a lot of writing but I hope this helps...I would have loved to have read this when I was first looking for answers.
“H3....built like **** but look pretty” lol
and I still love mine.

 

1st post and it's to reply to a 7+ year old thread.

Ooooooooooooo someone is gunna get a NECROBUMPING spanking


https://www.hummerforums.com/forum/n...bumping-23220/
READ: Old Threads/'Necro-Bumping'Do your part to keep the forums tidy, BEFORE you post, LOOK at the date the thread was started and the dates of the last few posts. Posting in old threads, or 'necrobumping' is generally discouraged in the subforums, since it can potentially create disjointed 'zombie' information; outdated posts with data which is no longer relevant due to the rolling nature of membership, changes in part numbers or technical service bullitens, recall information, part availability and sources, and combined with more recent posts reflecting more current circumstance.

"OLD Threads" are not weeks or even months old, OLD threads are 1, 2 and 3 year + OLD.

USE the SEARCH feature FIRST!

Rules of thumb

■If you have a question, start a new thread and link to the old if relevant.
■If you have something to add and judge that your information is related, but more up-to-date, start a new thread and link to the old if desired, but avoid duplicating effort by posting information already contained in the Archived Thread Section, sticky threads (at the top of the forum) and the old thread itself.

 

Why tack your Book long question on the end of an OLD azzed Thread?

BTW if you are still using the crappy OEM battery terminal connectors, you haven't fixed your problem, you just hid it for a while. Search that, avoid tacking on the end of OLD Threads.