P0E0A: W-phase low input and the Mazda M Hybrid fail-safe

In Mazda's documented M Hybrid integrated starter generator, P0E0A:00 identifies a W-phase current-sensor signal of 0.1 V or less. The phase name tells the technician which internal current measurement was rejected. It does not identify a wheel, a cylinder or an externally accessible low-voltage battery terminal.

Loss of hybrid support changes the complaint

The associated fail-safe stops supply from the M Hybrid battery and uses the 12 V battery for the vehicle's electrical devices. Regeneration and motor assist are inhibited. A driver may therefore report several missing hybrid functions even though the diagnostic entry names one phase sensor.

Those effects explain why treating each disabled function as a separate failed component is unhelpful. They are documented consequences of this fault response. They also limit continued operation: Mazda warns that depletion of the 12 V battery can eventually prevent further driving.

Establish whether the signal fault remains

The factory procedure saves snapshot data and distinguishes present from historical status. It rechecks an active complaint after an ignition cycle and at least 10 seconds. A past event goes through repeatability assessment, while recurring faults require communication diagnosis before the ISG decision is completed.

This is a shared phase-sensor diagnostic flow, not a separate W-phase disassembly chart. The manual supplies no applicable external wiring or connector diagram for this monitor and no individual sensor repair here. A qualified hybrid technician should interpret recurrence and perform any ISG work. The completion check also looks for other DTCs, so restored hybrid behavior and an empty single-code screen are not interchangeable evidence. Scope is the cited Mazda 3-era M Hybrid manual.

Source: Mazda workshop diagnostic page id140202300000, original manufacturer procedure publicly mirrored by Operation CHARM.