Code Definition

P0A91 — Drive motor B performance

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

About P0A91

P0A91 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P0A91 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 P0A91 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

Drive Motor B is the second electric machine in the drive system, commonly the secondary traction motor in a dual motor vehicle or a second motor generator, driven by its inverter or motor control unit under command of the hybrid or EV control module. DTC P0A91 sets when the module detects that Drive Motor B is not performing within its specified parameters, with actual torque output, rotational speed, current consumption, or feedback signals deviating from the expected values for the commanded operation. The cause may lie in the motor windings, the inverter that drives them, the rotor positio...

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