GM Service Manual Online
For 1990-2009 cars only

Removal Procedure

    Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  1. Disconnect the negative battery cable.
  2. Remove the air lines. Refer to Hose and Line Replacement - Nylon and Metal Compression in Air Brakes.

  3. Object Number: 156601  Size: SH
  4. Remove the 2 mounting bolts (2), 4 washers (3) and 2 nuts  (5).
  5. Remove the modulator (4).

Installation Procedure


    Object Number: 156601  Size: SH

    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.

    Important: It may be necessary to transfer the fittings from the old modulator to the replacement part.

  1. Install the modulator to vehicle using 2 mounting bolts (2), 4 washers (3) and 2 nuts (5).
  2. Tighten
    Tighten the modulator nuts (5) to 70 N·m (52 lb ft).

  3. Install the modulator electrical connector.
  4. Connect air lines to modulator valve. Refer to Hose and Line Replacement - Nylon and Metal Compression in Air Brakes.
  5. Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  6. Reconnect the negative battery cable.