header bg
8 arrow_forward 0 done arrow_forward 0 done_all

If your test of the tractor protection valve is successful,

A the tractor protection valve control (trailer air supply control) will pop out or go from "normal" to "emergency."
Explaination
When you test the tractor protection valve, the tractor protection valve control (also called the trailer air supply control) should pop out or go from from the "normal" to the "emergency" position. This shows that the tractor protection valve has closed automatically to keep the air pressure from falling too far.
B the parking brake valve will pop out.
C the low air pressure warning signal will come on.