GM Service Manual Online
For 1990-2009 cars only

Notice: 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.

Notice: Use care when handling the motor packs. Replace the motor packs if the motor packs are dropped or damaged during handling.

Important: Perform the Automated ABS brake motor-pack Diagnosis Test, when the disassembly of the brake modulator and motor-pack assembly was caused by an ABS hydraulic functional test that did not pass. Refer to the Scan Tool Diagnostics in Antilock Brakes. The Automated ABS brake motor-pack Diagnosis Test isolates the motor-pack or the brake modulator.

Important: A repair of the motor-pack is not authorized. Replace the motor-pack assembly.


    Object Number: 221843  Size: MH
  1. Perform the procedure called Gear Tension Relief Sequence.
  2. Remove the hydraulic modulator assembly. Refer to Brake Pressure Modulator Valve Assembly Replacement .
  3. Remove the 6 screws (5) that attach the gear cover (4).
  4. Remove the gear cover (4) from the brake motor-pack assembly (1).
  5. Remove the 4 screws (6) that attach the brake motor-pack assembly (1) to the hydraulic modulator (2).
  6. Remove the brake motor-pack assembly (1) from the hydraulic modulator (2).

Installation Procedure


    Object Number: 221843  Size: MH
  1. With the hydraulic modulator upside down, and the gears facing you, rotate each hydraulic 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-pack assembly. Replace the motor-pack assembly if the motor-pack assembly is dropped or is damaged during handling.

  3. Install the brake motor pack (1) to the hydraulic modulator. Align each of the 3 motor-pack assembly pinions with the modulator gears.
  4. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  5. Install the screws (6) that attach the brake motor-pack assembly (1) to the hydraulic modulator (2).
  6. Tighten
    Tighten the 4 head screws to 5 N·m (44 lb in).

  7. Install the gear cover (4) to the brake motor-pack assembly (1).
  8. Install the 6 screws (5) that attach the gear cover (4).
  9. Tighten
    Tighten the 6 screws to 4 N·m (36 lb in).

  10. Install the hydraulic modulator assembly. Refer to Brake Pressure Modulator Valve Assembly Replacement .
  11. Using the scan tool, perform the motor rehome procedure.
  12. Perform the Diagnostic System Check - ABS .