After supplying air to a newly coupled trailer and confirming normal air pressure, how does the manual say a driver should confirm the trailer's brakes are working before driving away?

Explanation

After supplying air and waiting for normal pressure, the manual has the driver shut the engine off so the brakes can be heard, then apply and release the trailer brakes, listening for the sound of the brakes moving when applied and air escaping when released, and watch the air pressure gauge for any sign of a significant leak, before starting the engine again. This is manual-only procedure, topic-scoped to 49 CFR 383.111(c)(1). An unlit ABS lamp confirms only that the ABS electronics report no malfunction, not that the base brakes are functioning. Driving a short distance to test under load is an unsafe, untaught test that risks a real failure at speed. The tractor protection valve's job is protecting tractor air supply, not verifying the trailer's brakes, so it cannot substitute for this check.

Source: 49 CFR 383.111(c)(1)