P0E03: U-phase current-sensor high input and the charging misconception

For the documented Mazda M Hybrid integrated starter generator, P0E03:00 means the U-phase current sensor's input signal has reached 4.9 V or more. A high sensor signal is not the same statement as excessive vehicle charging voltage. Replacing a 12 V battery or diagnosing overcharging solely from the word high would confuse the measured circuit with the electrical system it helps control.

Preserve the conditions before interpreting the code

Mazda's procedure begins with snapshot recording. It then asks whether the ISG reports a present malfunction. A currently active complaint is checked again after an ignition cycle and a wait of at least 10 seconds; a historical complaint enters a separate recurrence assessment. The source gives no duration requirement for the 4.9 V monitor itself.

These distinctions are useful when a scan report contains both a stored code and apparently normal current information. A normal observation now does not erase the earlier event, but the stored event also does not prove that the signal is continuously high.

An internal diagnosis still checks communication

The page lists an ISG malfunction as the possible cause and supplies no external wiring or connector diagram for this monitor. Its recurring-fault path nevertheless calls for CAN communication diagnosis before returning to the ISG decision. That is a reason to preserve the full module report instead of treating this as a standalone battery-charging code.

The diagnostic logic is shared with the other phase-current sensor faults; Mazda does not prescribe a unique U-phase repair here. Work and confirmation belong to a qualified hybrid technician. Loss of hybrid electrical support can leave the 12 V battery supplying the vehicle until depleted, so successful repair must include a complete fault check rather than a code erase alone.

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