For 1990-2009 cars only
- Block the wheels.
- Start the engine.
- Charge the system to the air compressor governor cut-out point.
- Stop the engine.
- Pull out the park control valve (cab mounted) knob and release the brake pedal.
- Verify that the spring brake chamber assemblies are applied.
- Push in the park control valve (cab mounted) knob.
- Verify that the spring brake chamber assemblies are fully released.
- Drain the front service air reservoir.
- Observe the dual air pressure gauge while the rear air reservoir is draining.
- 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.
- Remove the wheel blocks.
For models with trailer provision, refer to Parking Control Valve Operational Check .
If the park control valve knob does not pop out, overhaul or replace the park control valve (cab mounted).
