For 1990-2009 cars

1. Block the wheels.
2. Install accurate test gauges into the front and rear dual application valve circuits.
3. Start the engine.
4. Charge the air system to the air compressor governor cut-out point.
5. Stop the engine.
6. Depress the brake pedal to several positions between fully released and fully applied.
7. Check the delivered air pressure on the test gauges in order to see that it varies equally and proportionality with the movement of the brake pedal.

After a full brake application is released, the reading on the test gauges should fall off to zero promptly. The rear brake circuit delivery air pressure will be about 14 kPa (2 psi) greater than the front brake delivery air pressure with both service air reservoirs at the same pressure. This is normal for this valve.

8. If the dual application valve does not operate as described, overhaul or replace the dual application valve. Refer to Air Brake Application Valve Replacement or Air Brake System Description and Operation .
9. Drain the air reservoirs.
10. Remove the test gauges.
11. Start the engine.
12. Charge the air system to the air compressor governor cut-out point.
13. Stop the engine.
14. Check for proper brake operation.
15. Remove the wheel blocks.