For 1990-2009 cars only
- Block the wheels.
- Start the engine.
- Charge the system air pressure to the governor cut-out point.
- Pull the tractor park knob (if present) out.
- Disconnect the trailer service line hose coupling.
- Move the trailer brake control valve lever in order to fully apply the trailer service brakes.
- Hold a finger over the 1.6 mm (1/16 in) vent hole in the valve.
- Check for leakage at the hose coupling and the exhaust port.
- If leakage is excessive, replace the valve.
- Apply the trailer brake control valve lever.
- Turn the ignition ON and check for stoplamp operation.
- Release the trailer brake control valve lever.
- Check if there is pressure at the trailer service hose coupling.
- Check for leakage at the exhaust port.
- If leakage is excessive, replace the valve.
- Release the trailer brake control valve lever.
- Firmly apply the brake pedal.
- Check for leakage at the trailer air brake valve exhaust port.
- If leakage is excessive, replace the valve.
- Release the brake pedal.
- Drain all of the air from all of the lines and the reservoirs.
- Disconnect the air pressure test gauge and the service hose coupling.
- Set the parking brakes.
- Remove the wheel blocks.
