During which test should you pump down the service brake to test the air pressure system?

The correct answer involves the Low Air Pressure Alarm Test. During this test, it is crucial to pump down the service brake to reduce the air pressure in the system to ensure that the low air pressure warning device activates correctly. This helps confirm that the alarm and warning lights are functioning properly to alert the driver when air pressure falls below a safe threshold, which is essential for the safe operation of the vehicle and prevention of brake failure.

In this context, the Low Air Pressure Alarm Test specifically requires the action of pumping down the brakes to simulate a low-pressure scenario, allowing the driver to verify that the alarm engages as intended. This proactive check is vital in maintaining awareness of the system's operational limits and ensuring safety on the road.