GM Service Manual Online
For 1990-2009 cars only

Removal Procedure


    Object Number: 221843  Size: MH
  1. Remove the brake modulator assembly. Refer to Brake Pressure Modulator Valve Assembly Replacement .
  2. Remove the four Torx® head screws that retain both ABS brake solenoids from the hydraulic modulator assembly.
  3. Remove both brake solenoids from the hydraulic modulator assembly.
  4. Remove the Torx® head screws (5) attaching the gear cover (4).
  5. Remove the gear cover (4).
  6. Remove the four Torx® head screws (6) attaching the motor pack (1) to the hydraulic brake modulator (2).
  7. Remove the motor pack (1) from the hydraulic brake modulator (2).
  8. Important: Use care when handling the motor pack to ensure the motor pack connector is not damaged, or accidental intrusion of brake fluid into the motor pack does not occur. This may result in a premature failure of the motor pack.

    Important: Take care in handling the motor pack. If dropped or damaged during handling, the motor pack must be replaced.

  9. Remove the two brake modulator to master cylinder banjo bolts and the proportioning valve from the hydraulic brake modulator.
  10. Remove the two transfer tubes with the O-rings from the proportioning valve or hydraulic brake modulator.
  11. Remove the banjo bolt O-rings from the proportioning valve and the hydraulic brake modulator.

Installation Procedure

Important: When replacing the ABS brake modulator, install the three gears in the same location on the replacement brake modulator. Refer to Brake Modulator Gear Replacement .

No repair of the ABS brake modulator is authorized. Replace the ABS brake modulator as an assembly.

    Important: Use new transfer tube assemblies when assembling the proportioning valve to the hydraulic brake modulator. Be sure to properly install two O-rings on each transfer tube.


    Object Number: 221843  Size: MH
  1. Use the following procedure in order to install the two transfer assemblies:
  2. 1.1. Lubricate the transfer tube assembly O-rings with clean brake fluid.
    1.2. Install the transfer tube assemblies into ports of the ABS hydraulic brake modulator.

    Push the tube assemblies in by hand to the bottom of the ports.

  3. Lubricate the new banjo bolt O-rings with clean brake fluid.
  4. Install the banjo bolt O-rings into the ABS hydraulic brake modulator and the proportioning valve.
  5. Use the following procedure in order to install the proportioning valve onto the ABS hydraulic brake modulator
  6. 4.1. Insert the transfer tube assemblies into the proportioning valve ports.
    4.2. Hold the ABS hydraulic brake modulator and rock the modulator into position on the proportioning valve.
  7. Install two ABS hydraulic brake modulator to proportioning valve banjo bolts.
  8. Tighten
    Tighten the banjo bolts to 24 N·m (17 lb ft).

  9. With the ABS brake modulator positioned upside down, and the gears facing you, rotate each ABS brake modulator gear clockwise until movement stops.
  10. The procedure causes the following conditions:

    • The pistons are positioned very close to the top of the modulator bore.
    • The brake bleeding procedure is simplified.
  11. Install the ABS brake motor pack (1) onto the hydraulic brake modulator (2). Aligning the three motor pack gears with the modulator gears.
  12. Install the four Torx® head screws (6) that retain the motor pack (1) to the hydraulic brake modulator (2).
  13. Tighten
    Tighten the four Torx® head screws to 5 N·m (44 lb in).

  14. Install the gear cover (4) to the hydraulic brake modulator/motor pack assembly (2).
  15. Install the Torx® head screws (5) that retain the gear cover (4).
  16. Tighten
    Tighten the Torx® head screws to 4 N·m (36 lb in).

  17. Install the ABS brake solenoids to the hydraulic brake modulator/motor pack assembly.
  18. • Lubricate the solenoid seals with clean brake fluid.
    • Verify that the solenoid seal is properly positioned to each solenoid.
    • Position solenoids so that their electrical connectors will face the same direction prior to removal.
    • By hand, press down firmly on the solenoids until their flanges seat onto the hydraulic modulator.
  19. Install the four Torx® head bolts that retain the brake solenoids.
  20. Tighten
    Tighten the Torx® head screws to 5 N·m (44 lb in).

  21. Install the brake modulator assembly. Refer to Brake Pressure Modulator Valve Assembly Replacement .
  22. Perform the Diagnostic System Check