Code Definition

P0A90 (509) — Drive motor A performance

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Toyota

About P0A90

P0A90 is a generic (obd-ii standard) powertrain diagnostic trouble code recorded for Toyota vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0A90 is stored, the module has detected a plausibility fault — the measured value is in the electrical range but is not consistent with expected operating behaviour.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P0A90 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

On Toyota and Lexus hybrids the hybrid vehicle control ECU determines the rotational position of Motor Generator 2 (MG2), the traction motor known as Drive Motor A, from the MG2 resolver, a position sensor in the hybrid transaxle. This manufacturer subcode of P0A90 sets when the ECU receives abnormal or inconsistent resolver signals, so it cannot correctly interpret MG2 position and the phase angle no longer correlates with rotational speed as expected. Accurate rotor position is essential for controlling a three phase motor, so a resolver fault produces erratic or degraded MG2 drive. Symptoms...

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