P0A3F: Drive Motor A Position Sensor Circuit
What to do
Expect the car to protect itself firmly — possibly refusing to drive electrically at all. Insist the external wiring and connectors are tested before anyone opens or condemns the transaxle: the internal sensor is the rare failure, the harness to it is the common one. Orange-cable territory — hybrid-qualified workshop only.
What this code means
The drive motor's position sensor circuit has failed — the module has lost sight of where the rotor is.
This sensor is to the electric motor what the crankshaft position sensor is to the engine. The inverter creates torque by energising each of the motor's three phases at exactly the right instant relative to the rotor's magnets, and "the right instant" is defined by rotor angle. On most hybrids the sensor is a resolver — a small transformer arrangement with no electronics inside the transaxle, chosen precisely because it survives heat and oil that would kill anything cleverer.
Lose the angle and the inverter cannot commutate, so electric drive stops rather than degrades — the failure is binary in a way most sensor faults are not. On a full hybrid the car may refuse READY or run engine-heavy; the generator's resolver failing (P0A4B) can take engine starting with it.
The repair economics are lopsided and worth knowing before any quote. The resolver itself is inside the transaxle — a major job — but resolvers barely ever die; the wiring between the transaxle and the inverter fails constantly by comparison, and it is external, inspectable and cheap. A resolver condemned without the harness being load-tested first is the classic expensive mistake of this family.
Likely causes
Start here
- Chafed harness between transaxle and inverter · moderate
- Corroded or loose connector · easy
- Open circuit in sensor wiring · moderate
Less common
- Faulty motor position sensor · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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