GM Service Manual Online
For 1990-2009 cars only

Removal Procedure


    Object Number: 199151  Size: MH
  1. Apply the parking brake.
  2. Block the wheels.
  3. Drain all of the air reservoirs. Refer to Air Brake Reservoir Draining .
  4. Important: Tag the air lines for later installation.

  5. Remove the air lines at the inter-axle differential lock control valve. Refer to Hose and Line Replacement - Nylon Push-In Type Fitting .
  6. Remove the inter-axle differential lock control valve name plate screws (1).
  7. Remove the inter-axle differential lock control valve name plate (2).
  8. Remove the inter-axle differential lock control valve (3) from the instrument panel.
  9. Inspect the air lines for the following conditions:
  10. • Damage
    • Kinks
    • Wear
  11. Repair or replace the air lines as needed. Refer to Hose and Line Replacement - Nylon Push-In Type Fitting .

Installation Procedure


    Object Number: 199151  Size: MH
  1. Install the inter-axle differential lock control valve (3) into the instrument panel.
  2. Install the inter-axle differential lock control valve name plate (2).
  3. Notice: Refer to Fastener Notice in the Preface section.

  4. Install the inter-axle differential lock control valve name plate screws (1).
  5. Tighten
    Tighten the screws (1) until fully seated. Do not strip the inter-axle differential lock control valve name plate screws (1).

  6. Install the air lines at the inter-axle differential lock control valve. Refer to Hose and Line Replacement - Nylon Push-In Type Fitting .
  7. Start the engine. Charge the system to the air compressor governor cutout point.
  8. Stop the engine.
  9. Inspect for air leaks using a soap solution.
  10. Verify proper operation of the inter-axle differential lock.
  11. Remove the wheel blocks.