P0A47

What it means

P0A47 means the hybrid or electric vehicle control unit has detected a low voltage or signal level in the circuit of the position sensor for drive motor B. This sensor, often a resolver or similar device, tells the control unit the rotor angle and speed so it can time the motor current accurately. The code sets when the signal sits below the expected range, which points to a fault in the sensor, its wiring or the signal processing.

Symptoms

• Hybrid or EV system warning light on the dashboard, plus the malfunction indicator lamp
• Reduced power or limp-home mode
• Car refuses to enter ready mode or shuts down while driving
• Rough or jerky drive, or a noticeable loss of motor assistance
• Reduced regenerative braking or abnormal motor noise
• Engine running more than normal on a hybrid as the motor is limited

Possible causes

• Damaged wiring or poor connector contact in the motor B position sensor circuit (open circuit, short to ground, corrosion, chafed harness)likely
• Faulty drive motor B position sensor (resolver or equivalent)likely
• Water ingress or contamination in the motor housing connector or sensorpossible
• Faulty sensor supply or reference signal from the inverter or motor control unitpossible
• Mechanical damage or incorrect sensor alignment after motor or transmission workpossible
• Internal fault in the inverter or hybrid control modulerare

How to diagnose

1. Read all stored and pending codes and record the freeze frame data, noting any other motor, inverter or high voltage codes.
2. Check for relevant technical service bulletins and the manufacturer's procedure for this model, as sensor type and layout vary by vehicle.
3. Visually inspect the motor B position sensor harness and connectors for chafing, heat damage, corrosion, moisture and bent or pushed-back pins.
4. Only a technician trained in high voltage systems should go further: follow the manufacturer's isolation and safe-working procedure before touching any orange high voltage components.
5. Using live data, watch the motor B rotor position and speed values with the car at rest and when turned slowly, checking for dropouts or a flat low reading.
6. With the system isolated, test the sensor circuit for continuity, shorts to ground, and sensor coil resistance against the manufacturer's specification.
7. Check the supply and signal levels at the sensor connector against specification, and compare with a known-good reading where the model allows.
8. Clear the code and road test, rechecking live data to confirm the fault does not return.

How to fix

• Repair or replace damaged wiring and clean or replace corroded or loose connectors in the sensor circuit.
• Replace the drive motor B position sensor if it fails resistance or signal tests, and set it up to the manufacturer's procedure where required.
• Dry out and seal the affected connector or housing, and correct the source of water ingress.
• Correct sensor alignment or reassemble the motor correctly if the fault followed mechanical work.
• Replace or reprogram the inverter or control module only after confirming it is the fault, and only if an outdated calibration is a known cause for that model.

Can I keep driving?

Nearby codes

• P0A46GenericDrive Motor B Position Sensor Circuit Range/Performance
• P0A48GenericDrive Motor B Position Sensor Circuit High