You can confirm that a tractor protection valve is working properly by:

Question

You should test the tractor protection valve by allowing the air supply to properly charge, turning off the engine, then releasing air from the system by pressing the brake pedal several times. The tractor protection valve should move into its emergency position when psi drops to an unsafe level.

Accepted Answer

Releasing air with the brake pedal and waiting for the emergency signal to activate.

Answer

Disconnecting all glad hands.

Answer

Opening all of the vehicle's shut-off valves.