P25C5: Brake-unit internal temperature sensor low-voltage subcode

P25C5 broadly describes brake-booster temperature-sensor range/performance. Mazda's electronically controlled brake unit uses the full code P25C5:16 for voltage below specification in its internal temperature-sensor circuit.

Preserve the module and suffix

The :16 suffix and originating brake unit are essential context. This source lists an internal circuit short to ground or an internal open circuit as the possible causes. It does not identify an external ambient-temperature sensor, and it does not publish a numerical voltage threshold.

The temperature-sensor input being low is also different from proving that the brake unit is physically cold or overheated. The monitored fault concerns the electronics used to determine temperature. An engine-only reader that omits the suffix may conceal that distinction.

Repeatability precedes an assembly decision

Mazda's procedure clears and rechecks the brake-unit record, then assesses CAN communication if the same pending DTC returns. Its brake-unit replacement branch follows that repeatability and communication assessment. The page refers fail-safe details to another table, so this article does not infer which braking functions remain available.

Brake assistance requires qualified diagnosis with the exact vehicle procedure. Do not open the unit or probe its internal sensor based on this code. Completion includes review of other DTCs as well as the original fault. A code disappearing after erasure is not an independent test of brake-system performance or a safe-driving assurance.

Documented application

Mazda3 workshop manual 01/2019 onward, d9n1-1a-22d_ver10; ELECTRONICALLY CONTROLLED BRAKE UNIT. Verify exact vehicle specification; this is a Mazda application example. Mazda factory diagnostic page, mirrored by CHARM.