P0B16: Low voltage in the Mazda M Hybrid battery output monitor

P0B16 generally identifies hybrid battery voltage-sense B circuit low. Mazda's M Hybrid battery page specifies its 24-volt circuit monitor at battery terminal 2A.

READY state is part of the test

The measured terminal voltage must be below 10 V for three seconds while the battery is READY and its internal relay is on. P0A1F:09 must be absent. A voltage observed with the relay intentionally open is therefore not equivalent to the monitored condition.

The source lists a hybrid battery malfunction and inhibits i-stop. It does not provide an individual-cell low-voltage conclusion from this pack-terminal code. Cell voltage, pack output and the state of the internal relay are different diagnostic information.

History and vibration influence confirmation

Mazda distinguishes a present fault from a historical record and checks for P0AE3 after an ignition transition. Its repeatability guidance specifically notes that vertical vibration on an uneven road can expose the concern. That makes the captured operating context relevant to an intermittent output fault.

Any road confirmation must be appropriate and safe under professional supervision; the code is not an instruction to seek harsh road impacts. Do not open the hybrid battery or bypass its relay. Use the exact battery procedure to establish whether the low output recurs in READY, while retaining the related precharge and module-status records before selecting an assembly repair.

Documented application

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