Answer :
Final answer:
The tractor protection control valve should be in the normal position when checking the trailer emergency brake, ensuring that the system is set to maintain air pressure and engage the brakes in case of air pressure loss.
Explanation:
When you check the trailer emergency brake, the tractor protection control valve should be replaced in the C. Normal position. The reason for this is that in normal driving conditions, the valve should be in this position to maintain air pressure to the emergency brake system. If the system loses air pressure, such as in an air leak or disconnection, the emergency brakes will activate to stop the trailer, providing safety in case of a malfunction or separation.
