Perform a manual or pressure bleeding procedure. Refer to Hydraulic Brake System Bleeding. If the desired brake pedal height results are not achieved, perform the automated bleed procedure below. The procedure cycles the system valves and runs the pump in order to purge the air from the secondary circuits normally closed off during normal base brake operation and bleeding. The automated bleed procedure is recommended when air ingestion is suspected in the secondary circuits, or when the BPMV has been replaced.
The Auto Bleed Procedure may be terminated at any time during the process by pressing the EXIT button. No further Scan Tool prompts pertaining to the Auto Bleed procedure will be given. After exiting the bleed procedure, relieve bleed pressure and disconnect bleed equipment per manufacturers instructions. Failure to properly relieve pressure may result in spilled brake fluid causing damage to components and painted surfaces.
Automated Bleed Procedure
- Raise the vehicle on a suitable support. Refer to Lifting and Jacking the Vehicle.
- Remove all four tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation.
- Inspect the brake system for leaks and visual damage. Refer to Brake Pipe and Hose Inspection or Symptoms - Hydraulic Brakes. Repair or replace as needed.
- Inspect the battery state of charge. Refer to Battery Inspection/Test.
- Install a scan tool.
- Turn ON the ignition, with the engine OFF.
- With the scan tool, establish communications with the EBCM. Select Special Functions. Select Automated Bleed from the Special Functions menu.
- Bleed the base brake system. Refer to Hydraulic Brake System Bleeding.
- Follow the scan tool directions until the desired brake pedal height is achieved.
- If the bleed procedure is aborted, a malfunction exists. Perform the following steps before resuming the bleed procedure.
- When the desired pedal height is achieved, press the brake pedal in order to inspect for firmness.
- Remove the scan tool.
- Install the tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation.
- Inspect the brake fluid level.
- Road test the vehicle while inspecting that the pedal remains high and firm.
Brake Pressure Modulator Valve Assembly Replacement
- Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection.
- Disconnect the electronic brake control module (EBCM) connector (1).
- Remove the brake pipes from the brake pressure modulator valve (BMPV) assembly.
- Plug the brake pipes.
- Loosen the mounting nuts (2) on the BPMV assembly (1).
- Position the brake pipes aside far enough to allow for lifting the BPMV assembly from the mounting bracket. It may be necessary to loosen the brake pipes on the master cylinder to allow for moving those pipes out of the way.
- Remove the BPMV assembly from the mounting bracket.
Take care not to allow air into the hydraulic unit or into the brake pipes from the master cylinder. If air gets into the hydraulic unit, it will require a bleeding procedure using a scan tool programmed for the ABS 5.3 system. As long as no air enters the hydraulic unit, a simple bleeding procedure is all the system will require.