GMC Sonoma Service Brakes, Hydraulic Problems

Model years: 2000

Problem: Vehicle description: light duty pickup trucks equipped with 4-wheel disc brakes. Some of these vehicles have an antilock brake system (abs) motor containing an out-of-specification spring clip. This clip could allow the motor bearing to become misaligned. If misalignment occurs, eventually the abs would be non-functional.

Risk: The base brakes would remain fully functional, but the dynamic rear proportioning (drp) system, which optimizes front to rear brake balance, would become inoperative.

Fix: Dealers will replace the brake pressure module valve assembly.

Model years: 2000

Problem: Vehicle description: s -trucks equipped with 2 wheel drive. These vehicles may have had the right-hand antilock brake system (abs) module feed pipe and/or brake crossover pipe tube nuts tightened without seating the pipe-flared-ends enough to withstand normal assembly and vehicle inputs without partially unseating. This does not comply with requirements of fmvss no. 105, "hydraulic service brake normal, emergency, and park braking performance."

Risk: If this occurred, the seating seal could be broken during vehicle assembly, or from early road inputs or brake fluid cycling, and a leak could occur increasing the brake stopping distance.

Fix: Dealers will inspect the brake pipe union for signs of brake fluid, and if necessary, install a new brake pipe union.

Model years: 1995, 1996

Problem: Vehicle description: certain 4-wheel drive pickup trucks and sport utility vehicles equipped with abs (antilock braking system) manufactured from september 1989 through august 1996. Under certain driving conditions the switch which signals the abs system whether the vehicle is in 2-wheel or 4-wheel drive can malfunction causing increased stopping distances during abs stops while in the two-wheel drive mode.

Risk: If this occurred at a time when minimum stopping distance was required, a vehicle crash could occur without prior warning.

Fix: Dealers will replace or repair the 4-wheel/2-wheel drive switch.

Model years: 1998

Problem: Vehicle description: light duty pickup trucks and multi-purpose passenger vehicles. A fatigue fracture of the rear axle right-hand brake pipe can occur causing a slow brake fluid leak resulting in a soft brake pedal. If the brake pipe breaks, the driver would experience a sudden drop in the brake pedal, the instrument panel brake light would illuminate, and there would be a loss of rear brake performance.

Risk: Partial loss of braking at a time when minimum stopping distance was required could result in a vehicle crash.

Fix: Dealers will inspect and replace the brake pipe.

Model years: 1996, 1997

Problem: Vehicle description: light duty passenger pickup trucks equipped with 4.3l engines. The front brake line can contact the left-hand side of the engine oil pan causing the brake line to wear to the point of brake fluid loss during brake application.

Risk: Brake fluid loss can reduce braking effectiveness and increase stopping distances resulting in a vehicle crash without prior warning.

Fix: Dealers will inspect the clearance between the oil pan and the brake line. If the clearance is 6mm or less, dealers will install an additional brake line clip and if there was contact between the oil pan and brake line, the front brake line will be replaced.