Answer :
Final answer:
To test the tractor protection valve, one should check for air exhausting from the trailer supply line when the trailer air supply valve is closed (pulled out), indicating a malfunction.
Explanation:
To test the tractor protection valve, the correct procedure is to check for air exhausting from the: b) trailer supply line with the trailer air supply valve closed (pulled out). This is because when the trailer air supply valve is closed, it should activate the tractor protection valve, which prevents air from leaving the tractor and going to the trailer. If air exhausts from the trailer supply line when the valve is closed, this indicates a malfunctioning tractor protection valve, which is a critical safety issue that needs to be addressed.
