GM Service Manual Online
For 1990-2009 cars only
  1. Block the wheels.
  2. Start the engine.
  3. Charge the system to the air compressor governor cut-out point.
  4. Stop the engine.

  5. Object Number: 227705  Size: SH
  6. Push down the trailer air brake control valve lever to the full off position.
  7. Inspect the valve body and the exhaust port for any air leakage.
  8. If any air leakage is present, replace the trailer air brake control valve.

  9. Pull up the trailer air brake control lever to the full on position.
  10. Inspect the valve body and the exhaust port for any air leakage.
  11. If any air leakage is present, replace the trailer air brake control valve.

  12. Remove the wheel blocks.