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.

Notice: Do not allow gear to turn while removing the retaining nut, since the modulator piston can hit the top of the modulator bore, damaging the piston. Place a screwdriver through the holes in the gears (not between the gears) into the recessed hole in the modulator base. This will prevent the gear from turning, aiding in gear removal.

Important: Do not repair damaged motor packs or brake modulators. Other than modulator drive gears replacement, repair of the motor pack and brake modulator assemblies is not authorized. Do not oil or lubricate the gears on the motor pack.

  1. Remove the Brake Modulator Assembly. Refer to Brake Pressure Modulator Valve Assembly Replacement in this section.

  2. Object Number: 221843  Size: MH
  3. Remove the Torx® head screws (5) that attach the gear cover (4).
  4. Remove the motor pack to modulator Torx® head screws (6).
  5. Important: Use care when handling the motor pack. Replace the motor pack if the motor pack is dropped or damaged during handling.

  6. Separate the motor pack (1) from the Hydraulic Modulator (2).

  7. Object Number: 165947  Size: SH
  8. Remove the three modulator drive gear retaining nuts.
  9. Remove the gears from the modulator.

Installation Procedure


    Object Number: 165947  Size: SH
  1. Position the modulator drive gears onto the modulator drive shaft.
  2. Notice: Do not allow gear to turn while removing the retaining nut, since the modulator piston can hit the top of the modulator bore, damaging the piston. Place a screwdriver through the holes in the gears (not between the gears) into the recessed hole in the modulator base. This will prevent the gear from turning, aiding in gear removal.

  3. Install the three gear retaining nuts.
  4. Tighten
    Tighten the nuts to 8.5 N·m (76 lb in).

    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.


    Object Number: 165951  Size: SH
  5. With either of the modulators positioned upside down, and the gears facing your, rotate each ABS brake modulator gear counterclockwise until movement stops.
  6. Rotating the modulator gears will cause the following conditions:

    • The pistons on the ABS brake modulator will be positioned very close to the top of the modulator bore.
    • The brake bleeding procedure is simplified.

       Important: Use care when handling the motor pack. Replace the motor pack if the motor pack is dropped or damaged during handling.


    Object Number: 221843  Size: MH
  7. Position the motor pack (1) onto the modulator, aligning the three motor pack gears with the modulator gears (3).
  8. Install the motor pack to the modulator Torx® head screws (6).
  9. Tighten
    Tighten the Torx® head screws to 5 N·m (44 lb in).

  10. Install the gear cover (4) onto the modulator with Torx® head screws (5).
  11. Tighten
    Tighten the Torx® head screws to 4 N·m (36 lb in).

  12. Install the Brake Modulator assembly into the vehicle. Refer to Brake Pressure Modulator Valve Assembly Replacement in this section.
  13. Perform the Motor Rehome Procedure.
  14. Perform the Diagnostic System Check - ABS .