GM Service Manual Online
For 1990-2009 cars only
  1. Start the engine.
  2. Charge the system air pressure to the governor cut-out point.
  3. Have an assistant apply and release the brake pedal several times.

  4. Object Number: 202605  Size: SH
  5. Check that a spurt of air occurs at the exhaust port.
  6. Clean or replace or overhaul the valve (2) if there is no air at the exhaust port. Refer to Automatic Level Control Air Dryer Replacement or Air Brake System Description and Operation .