Symptoms
A SERVICE 4WD message, mode lights that keep flashing, shifts that take minutes, or a bang followed by no 4HI or 4LO at all.
The fix, step by step
- Scan the codes first.
- Clean or check the dash buttons, then check the encoder motor on the transfer case and its wiring.
- Owners warn that remanufactured and non-OEM motors are 'rubbish'.
- One owner says the usual failure is the contact ring inside the encoder, sold separately.
- If the case banged and stopped working, the plastic shift fork has probably broken: drop the transfer case, fit an aluminum fork and refill with fresh fluid.
Tools & part numbers
- Scan tool that reads transfer-case codes
- transmission jack
- seal kit
- fluid pump.
Where to buy the parts
Transfer case motor / encoder (catalog, 2005 H2)RockAuto ↗
Transfer case shift fork (catalog, 2005 H2)RockAuto ↗
Transfer case control module (catalog, 2005 H2)RockAuto ↗
Hunting a used or discontinued part? Search eBay Motors for AM General Hummer H2 parts →
Rated for a competent home mechanic with a decent tool kit. Confirm torque figures, fluids and procedures against the factory service manual for your VIN, support the truck on stands rather than a jack, and work at your own risk (disclaimer). Some parts links are affiliate links, which pay us a small commission at no cost to you.