Practice question

On the Ohio CDL Combination Vehicles test, what does the tractor protection valve do?

Lubricates the fifth wheel
Closes off the tractor air supply if trailer air pressure drops too low, preserving brake air for the tractor
Increases air pressure to the trailer
Operates the trailer ABS

Answer: B — Closes off the tractor air supply if trailer air pressure drops too low, preserving brake air for the tractor

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