For 1990-2009 cars

1. Block the wheels.
2. Apply the parking brake.
3. Disconnect the line or plug from the valve's supply and delivery ports.
4. Install the test air pressure gauges.
5. Drain the valves on the supply and the delivery ports.
6. Start the engine.
7. Charge the air supply to full pressure.
8. Turn off the engine.
9. Exhaust the pressure from the delivery side slowly while watching the gauges.

Both gauges will show a pressure loss until the valve's closing pressure is reached. The valve should close within 34 kPa (5 psi) of the rated pressure.

10. If the valve does not close within these specifications, replace or overhaul the valve (4). Refer to Pressure Protection Valve Replacement or Air Brake System Description and Operation .