Before a trip, you should ensure that air flows to all trailers by:

Before a trip, ensure that air in the air brake system reaches all trailers. Do this by waiting for air pressure to build, then sending air to both the emergency and service lines and opening the shut-off valves on the rear of the last trailer. If air escapes from the shut-off valves at the rear of the combination, the air is being supplied to the entire vehicle.

Wait, before you go

Ace Your California CDL Written Test with our Guaranteed Cheat Sheet