I've been looking at the boards for awhile after the 'Serv 4wd' warning displayed on the Instrument Panel.

I tried reversing round in circles and then I was able to briefly switch between 4wd high, high lock, and lo lock. When I switched from high to lo lock there was a clunk sound, but after that, it was absolutely fine and the warning light went off.

I dorve half a mile down the road, and the light came back on again!

Any body have any ideas? Loose wire, sticky buttons?

 

possible plastic shift fork trouble. search for tc case/fork,etc. there was a lot of that trouble last yr/2. mostly 06,h3. just a guess

 

Yes, this sounds very possible. Although I live in London UK, I wonder if my local GM stealer will be able to get me a price. If they can't is there anybody that can get parts in the US, and would be willing to send it over. May be able to do a Paypal payment?

I thought i had been lucky when she switched twice through the cycle. At least she's stuck in 4wd High, I'm not noticing any driving difference at all, so assume I'm not causing any dmage to the t-case??

Regardless of whether it is the fork or not, I may as well get it changed!

Thanks for the reply Tom, have printed off a picture from a thread so my mechanic knows what to look for.

 

yeah,glad u found it,when i search i find nuttin!!

 

Your issue could be multiple things. The 4x4 electronic controler, shift fork, one of your 4x4 control buttons is stuck or you may just need to give the BCM a quick refresh (BCM brain fart per F5fstop).

What year is your H3?

 

i actually have a spare transfer case switch for the adventure package if this is your problem?

 

The year is important. The plastic shift fork was used in 06 and into early 07 only.

I believe the T Case shift actuator throws that message when it has issues more often or earlier (if you will) than the fork. It could be many things that causes it.

 

Problem solved, but am very angry!!

I took the Hummer to a specialist in London. If anybody wants their name I will IM it over to you. They were fantastic, with almost 40 years in the business dealing with America Cars!

However, I had a bespoke stereo installed (by a different company) awhile back, and it turns out that when they installed the head unit, they bent one of the pins used for controlling the 4WD mode on the dash! This is what caused her to lock in 4WD high!

So fortunatley, no mechanical issues, no dodgy fork, purely an electrical issue, and sorted within a couple of hours.

@ Doc Olds, year is an 06 model, and UK GM dealer wants 30 GBP, approx 48USD for the aluminum part! I think I may source in the states, and get it sent over!

I think I'll get them to install it during my next full service.

Thanks again for all the help!