For 1990-2009 cars

1. Block the wheels.
2. Start the engine.
3. Charge the system air pressure to the governor cut-out point.
4. Pull out the trailer air supply knob (3).
5. Pull out the system park knob (1).
6. Apply a soap solution to the exhaust vent and around the base of the trailer air supply knob (3).
7. Verify that leakage is less than a 25 mm (1 in) bubble in 5 seconds. If not, replace the valve. Refer to Trailer Brake Supply Valve Replacement or overhaul the valve. Refer to Air Brake System Description and Operation .
8. If the leakage exceeds these limitations, replace the valve. Refer to Trailer Brake Supply Valve Replacement or overhaul the valve. Refer to Air Brake System Description and Operation .
9. Push in the trailer air supply knob (3).
10. Apply a soap solution to the exhaust port.
11. Check that the leakage is less than a 25 mm (1 in) bubble in 5 seconds.
12. If the leakage exceeds these limitations, replace the valve. Refer to Trailer Brake Supply Valve Replacement or overhaul the valve. Refer to Air Brake System Description and Operation .
13. Set the parking brake.
14. Remove the wheel blocks.