Pinpoint Test G: Testing
- G1 CHECK BASE BRAKE COMPONENTS
- Visually inspect the brake lines from the hydraulic control unit (HCU) to the wheel cylinders.
- Visually inspect the calipers and the brake components.
- Are any of these components damaged or leaking?
- Yes : REPAIR as necessary. REFER to BRAKE SYSTEM-GENERAL INFORMATION to continue diagnosis of the base brake system.
- No : GO to G2.
- G2 CHECK FOR LEAKING DUMP VALVE
- Key in START position.
- Remove the rubber caps from the two HCU low pressure accumulators and insert a clean steel implement (such as a paper clip) into each low pressure accumulator.
- Have an assistant press hard on the brake pedal while observing the steel implements.
- Do any of the steel implements move out 12.7 mm (0.5 in) or more?
NOTE: A leaking dump valve is similar to the master cylinder bypass condition. It is important that the pedal be quickly and forcefully applied to rule out the master cylinder bypass as a cause. Typically a master cylinder bypass occurs only at low pedal pressure rates and low tire pressures.- Yes : INSTALL a new HCU. REFER to HYDRAULIC CONTROL UNIT (HCU) .
- No : System is operating correctly at this time. REMOVE the steel implements and INSTALL the rubber caps. CLEAR the DTCs. DRIVE the vehicle over rough roads. REPEAT the self-test. TEST the system for normal operation.