When would the low air pressure warning buzzer not sound when below 60 psi on the M915?

Answer: B — When the truck is set to blackout drive

The low air pressure warning buzzer in the M915 functions to alert the operator when air pressure falls below 60 psi, a critical threshold for safe operation. The scenario where the warning buzzer does not sound is when the truck is set to blackout drive. In blackout drive, the vehicle is configured to operate with minimal lighting to maintain a low visibility profile, especially during night operations or in combat situations. This mode includes certain adaptations to electrical systems and may also affect alarms or indicator functions to avoid drawing attention. Adjusting for blackout drive can lead to changes in how and when warning systems are activated, which is why the low air pressure warning buzzer might not sound in this instance despite the pressure being critically low. Other factors, like the truck being in reverse, the engine being off, and the parking brake being engaged, do not disable the buzzer; they might still allow it to function normally in those conditions, maintaining safety protocols for air pressure awareness.