Code Definition

P0A4D (255) — Generator position sensor signal low

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

About P0A4D

P0A4D 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 P0A4D is stored, the module has detected a signal or supply voltage lower than the expected operating range; and a sensor-related fault — the reported value from the named sensor is out of spec.

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 P0A4D 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 hybrid vehicles the generator, designated MG1, uses a resolver position sensor to report rotor angle to the inverter assembly and Power Management Control ECU for control of charging, engine starting, and the power split function. DTC P0A4D sets when the ECU detects that the voltage amplitude of the sine or cosine output from the MG1 resolver is below its calibrated threshold. A low signal indicates weak resolver output, usually caused by high resistance, an open or short to ground, or a weak excitation feed, which prevents accurate rotor position detection. With unreliable...

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