Please Help. 2008 Hummer H3 Alpha

[NorseVikinAEsir]

I have abs fault, service stabilitrak, traction control messages and I can't get it to shift out of 4 Low. Also, barely any brakes with brake pedal not consistent. I changed the encoder motor and tried many of the tips and tricks on different forums, any ideas or help would be greatly appreciated, thanks.

 

[Jeepwalker]

Hmmmm ...that's frustrating! Vehicle start ok? Almost sounds like a bad ground/s or battery ..bad body/frame grounds. Some of the grounds on my rig were rusty I had to clean. Modern vehicles are really finicky on getting clean power. And since electrons flow from neg->pos ...it can cause funny conditions. I would start by checking/wiggling your battery connections.

Are you stranded right now? Or is the vehicle at your house/home? Do you have a scanner to check codes? Or swing by Autozone for a free scan if you get going. How's the brake switch?

 

[alrock]

You can disconnect the encoder motor and shift it manually. I know they make a tool for that, but I believe it can be done by pliers or similar. Here's some info: https://hummer4x4offroad.com/forum/...abs-will-block-your-tcase-from-shifting.9261/

When you press the buttons on the 4wd shift control, do they flash light they are trying to make a change?

But, it's quite possible the issues are linked. The brakes may be the key. First, I would verify that all of the ABS sensors are intact and are not disconnected or have any broken wires. As you can see in the above thread maybe one is bad and it might take an advanced diagnostic tool to figure out which one. Next, I would try bleeding the brakes. Start with the rear and do all four. Put a quart of DOT3 through there. Note that the engine must be on in the H3 to bleed the brakes. Bleeding them will remove any air in the lines, or deteriorated fluid. You might also find a defective caliper or other issue at one of the corners that's causing the ABS issue. I would pull off each caliper one by one and inspect them. Since you're in PA rust could be an issue, or deteriorated rubber components.

Do not step on the brake pedal with the calipers unbolted from the truck. You can overextend the pistons and cause ABS issues. Trust me on this one.

Of course it could be two different issues where there's a brake issue and maybe a worn shift fork in the transfer case. Have you changed the fluid in the transfer case? If so, what color was it - red, blackish, bright silver? Any chunks or excessive shavings?

 

[H3nightrod]

I had this issue before.
Try this
Turn ignition on but don’t start. Select 4H and wait for it to shift. Once it’s in 4H start the truck. I don’t recall if it was in Neutral or in park.
Hope this helps.

 

[atvspeed4]

It sounds like the brake booster pump crapped out. There is a little pump and accumulator that while rare, can fail. If it cannot maintain sufficient pressure the system goes into fault and will disable traction control and transfercase from shifting. People sometimes cook them while bleeding brakes after a line replacement. I dont think anything is wrong with your transfercase or encoder motor but without a tech 2 and going through methodical diagnostic I cannot tell.

 

[H3Hummer]

What about you T Case shift fork ? did you replace the OEM pvc , cause they go bad with the years and slip , so they let the T case stuck in the last 4x4 mode you selected. I replace mine with the AC Delco Aluminum shift fork and never had issues.