Certain sport utility vehicles, pickup trucks, and passenger vans fail to comply with the requirements of federal motor vehicle safety standard no. 135, "Passenger Car Brake Systems". Some of these vehicles were produced with an out-of-specification brake hydro-boost housing relief valve bore.

Consequently, the valve o-ring seal may fracture. Steering efforts may be slightly increased while braking or parking. Under certain driving conditions, a fractured seal may require a slight increase in the applied brake pedal effort to achieve the same vehicle deceleration rate as prior to the seat fracture.

GM has not yet provided a remedy for this campaign. Owner notification is expected to begin during the second quarter of 2004. Owners should contact Hummer at 1-866-486-6376.

Certain trucks, sport utility vehicles, and vans equipped with Bosch hydro-boost brake assemblies, the hydraulic brake booster pressure accumulator may crack and separate from the hydro-boost assembly during normal operating conditions.

If a separation occurred and the hood of the vehicle were open, fragments from the accumulator could cause injury to people in the immediate area. The presence of this crack or fractured surface could allow the hydraulic fluid to leak from the accumulator circuit of the booster assembly. The loss of fluid would cause increased steering and braking effort and a crash may occur without prior warning.

Dealers will test the hydro-boost assembly for functional operation of the two-function valve. If the hydro-boost assembly fails the test, dealers are to replace the assembly. The recall is expected to begin during March 2005. Owners should contact Hummer at 1-800-732-5493.