GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1999 🢒 Montana 🢒 Brakes 🢒 Antilock Brake System 🢒 ABS Motor Pack Replacement

Removal Procedure

    Object Number: 183883 Size: SH

    Important: If the disassembly of the modulator/master cylinder assembly was caused by an ABS or TCS 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 ABS motor pack is authorized. Replace as an assembly.

  1. Remove four brake pipes (5).
  2. Disconnect the brake fuild level indicator sensor connector (2).
  3. Disconnect two brake solenoid valve electrical connectors (1), (3).
  4. Disconnect the ABS brake motor pack 6-way electrical connector (6).
  5. Remove the two nuts (8) attaching the ABS brake modulator/master cylinder assembly (7) to the vacuum booster (4).

    6. Object Number: 183893 Size: MH
  6. Remove the two Torx® head screws (4).
  7. Remove the gear cover (3).
  8. Remove the four Torx® head screws (5) that attach the motor pack (1) to the ABS modulator assembly.

    9. 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 pack. Replace the motor pack if dropped or damages during handling.

  9. Remove the motor pack assembly (1).

Installation Procedure

    Object Number: 155168 Size: SH
  1. With either of the modulators positioned upside down, rotate each ABS brake modulator gear counterclockwise until movement stops.
  2. The above procedure will cause the following conditions:
    3. • The pistons on the ABS brake modulator will be positioned very close to the top of the modulator bore.
    • The brake bleeding procedure becomes simplified.

    Object Number: 183893 Size: MH

    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 motor pack assembly (1) to the modulator assembly (6).

    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.

  4. Install four Torx® head screws (4).

    5. Tighten
    Tighten the Torx® head screws to 4.5 N·m (40 lb in).

  5. Install the gear cover (3) onto the modulator/brake master cylinder assembly.
  6. Install the two Torx® head screws (4).

    7. Tighten
    Tighten the Torx® head screws to 4 N·m (35 lb in).


    Object Number: 183883 Size: SH
  7. Install two nuts (8) attaching the ABS brake modulator/master cylinder assembly (7) to the vacuum booster (4).

    8. Tighten
    Tighten the Torx® head screws to 27 N·m (20 lb ft).

  8. Install four brake pipes (5) onto the ABS modulator/master assembly (7).

    9. Tighten
    Tighten all four tube nuts to 24 N·m (18 lb ft).

  9. Connect the ABS motor pack 6-way electrical connector (6).
  10. Connect the brake fuild level indicator sensor electrical connector (2).
  11. Connect two brake solenoid valve electrical connectors (1), (3).
  12. Bleed the system. Refer to Hydraulic Brake System Bleeding in Brakes.