For 1990-2009 cars

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. Pull out the park control valve, cab mounted, knob and release the brake pedal.
6. Verify that the spring brake chamber assemblies are applied.
7. Push in the park control valve, cab mounted, knob.
8. Verify that the spring brake chamber assemblies are fully released.
9. Drain the front service air reservoir.
10. Observe the dual air pressure gauge while the rear air reservoir is draining.
11. Verify that the park control valve, cab mounted, pops out when the air pressure drops below 276 kPa (40 psi) on models without trailer provisions.

For models with trailer provision, refer to Parking Control Valve Operational Check .

If the park control valve knob does not pop out, overhaul. Refer to Air Brake System Description and Operation or replace the park control valve, cab mounted. Refer to Instrument Panel Mounted Air Brake Park Control Valve Replacement .

12. Remove the wheel blocks.