When checking the trailer emergency brakes, the tractor protection control valve should be in which position?

The tractor protection control valve should be in the "Emergency" position when checking the trailer emergency brakes. This setting is crucial because it allows the trailer's emergency brake system to engage properly, ensuring that the brakes are functioning as intended.

In the emergency position, the valve directs air flow to the emergency brakes, which helps check their responsiveness and effectiveness. This is a vital safety step; if the valve were left in another position, it might prevent the brakes from engaging or providing false results about their condition. By using the emergency setting, you can verify that the emergency brakes will activate correctly if needed, enhancing overall safety during vehicle operation.