Workshop Manuals Factory service & repair Hummer

Hummer common faults and how to fix them

Faults that are well known on Hummer models we hold manuals for: what the owner notices, what causes it, and the pages in our manuals that cover the repair.

Hummer H2 brake recall: Hydro-Boost accumulator can crack

Symptoms

The steering and brake pedal suddenly become much heavier, because hydraulic fluid has leaked from the brake booster's accumulator circuit. There may be power steering fluid around the booster on the bulkhead.

Cause

NHTSA recall 05V043000 covers certain trucks, SUVs and vans with Bosch Hydro-Boost brake assemblies, including the Hummer H2. Hydro-Boost uses power steering fluid pressure to assist the brakes. Its pressure accumulator could crack and separate from the booster in normal use. If that happened with the bonnet open, fragments could injure people nearby, and the lost fluid increases steering and braking effort.

Fix

Check with a GM dealer that the recall has been carried out. Don't work on the booster with the engine running, and check the area around the accumulator for cracks and fluid leaks. The Hummer H2 Hydro-Boost recall notice gives the details. If the steering or brakes become heavy, stop as soon as it is safe and have the booster and power steering fluid level checked.

Repair instructions on this site

Sources: NHTSA recall 05V043000.

Hummer H2 washer fluid heater recalls: overheating, smoke and fire risk (2006–2009)

Symptoms

A burning smell or smoke from the front of the engine bay, other electrical features playing up, or the heated washer system not working. In some cases there was a fire.

Cause

NHTSA recall 08V441000 covers 857,735 GM vehicles, including the 2006–2008 Hummer H2, with the heated windscreen washer fluid system. A short circuit on the heater's printed circuit board could overheat the control circuit's ground wire. GM's first remedy added a harness with an in-line fuse. Recall 10V240000 followed in 2010, after new reports of thermal incidents on the heater modules, and covered models up to 2009.

Fix

Check with a GM dealer that both recalls have been done. If there is any smell of burning or smoke from the area of the washer heater, disconnect the battery and don't use the vehicle until it has been checked. The Hummer H2 washer heater recall and the 2010 follow-up recall notices give the details and affected models.

Repair instructions on this site

Sources: NHTSA recalls 08V441000 and 10V240000.

Hummer H3 transmission: P0894 and P1870 slipping codes

Symptoms

The check engine light comes on with P0894 or P1870 (transmission component slipping). Engine revs may rise slightly at a steady cruise as the torque converter clutch slips.

Cause

A GM bulletin covering the H3's automatic gearbox explains that these codes have different root causes. Slip of about 100 to 400 rpm at a steady light load usually means the torque converter clutch isn't applying, for example because of a cracked TCC enable solenoid, a plugged TCC apply orifice in the pump (especially on low-mileage vehicles), or a converter clutch valve that sticks. Slip above about 400 rpm usually points to a slipping clutch or band.

Fix

Check the fluid level and condition first. Then use a scan tool to measure the slip speed at a steady cruise, as the Hummer H3 transmission bulletin describes, to decide whether the fault is in the converter clutch circuit or inside the gearbox. Follow its checks for the TCC enable solenoid, the pump orifice and the converter clutch valve before replacing the gearbox.

Repair instructions on this site

Sources: GM service bulletin, DTC P0894 and P1870 diagnostic information.