GM Service Manual Online
For 1990-2009 cars only

Removal Procedure

Caution: To help avoid personal injury, due to a retained load on the brake modulator, the Gear Tension Relief function of the scan tool must be performed prior to removal of the ABS brake modulator assembly.


    Object Number: 221843  Size: MH
  1. Remove the brake modulator assembly. Refer to Brake Pressure Modulator Valve Assembly Replacement in this Section.
  2. Remove the Torx® head screws (5) that attach the gear cover (4).
  3. Remove the gear cover (4) from the brake modulator.
  4. Remove the Torx® head screws (6) that attach the brake motor pack (1) to the brake modulator (2).
  5. Remove brake motor pack (1) from the brake modulator (2).

Important: Use care when handling the motor pack to avoid damaging the motor pack connector. Make sure brake fluid does not accidentally intrude into the motor pack. Brake fluid in the motor pack may cause a premature failure of the motor pack.

Important: Use care when handling the motor packs. Replace the motor packs if the motor packs are dropped or damages during handling.

Important: If the disassembly of the modulator/master cylinder assembly was caused by an ABS or hydraulic functional test that did not pass, the Automated ABS brake motor pack Diagnosis Test should be performed. Refer to Scan Tool diagnostics in Antilock Brakes. The Automated ABS brake motor pack Diagnosis Test isolates the motor pack or brake modulator.

No repair of the motor pack is authorized. Replace as an assembly.

Installation Procedure


    Object Number: 221843  Size: MH
  1. With the brake modulator upside down, and the gears facing you, rotate each brake modulator gear counterclockwise until movement stops. this procedure will position the pistons very close to the top of the modulator bore, simplifying the brake bleeding procedure.
  2. Important: Use care when handling the motor packs. Replace the motor packs if the motor packs are dropped or damaged during handling.

    Align each of the three motor pack pinions with the modulator gears.

  3. Install the brake motor pack (1) to the brake modulator (2).
  4. Install the Torx® head screws (6) that attach the Brake Motor Pack (1) to the Hydraulic Modulator (2).
  5. Tighten
    Tighten the Torx® head screws to 5 N·m (44 lb in).

  6. Install the gear cover (4) to the brake modulator (2).
  7. Install the Torx® head screws (5) that attach the gear cover (4).
  8. Tighten
    Tighten the Torx® head screws to 4 N·m (36 lb in).

  9. Install the brake modulator assembly. Refer to Brake Pressure Modulator Valve Assembly Replacement in this Section.
  10. Using the scan tool, perform the Motor Rehome Procedure.
  11. Perform the Diagnostic System Check