P0A45

What it means

P0A45 is the generic code for a fault in the Drive Motor 'B' position sensor circuit on a hybrid or electric vehicle. The motor position sensor, usually a resolver, tells the inverter or motor control unit the exact rotor angle so it can time the current to the motor. The code sets when the signal is missing, out of range, noisy or implausible compared with what the control unit expects. Exact sensor type, wiring and strategy vary by model, so check the manufacturer's data for the vehicle.

Symptoms

• Hybrid or EV system warning light on the dashboard
• Reduced power or limp mode
• Vehicle will not go into READY mode or will not move
• Engine or motor running roughly, or the drive system shutting down while driving
• Judder or surging under acceleration
• Poor efficiency, with the engine running more than normal on a hybrid

Possible causes

• Damaged, corroded or loose wiring or connector at the motor position sensor circuitlikely
• Faulty motor position sensor (resolver) or its stator or rotor alignment has shiftedpossible
• Electrical interference or poor shielding or earthing of the sensor harnesspossible
• Fault inside the inverter or motor control unit's sensor interfacepossible
• Chafed harness shorting to earth, to supply or to other wires near the motor or gearboxpossible
• Mechanical damage to the motor or its housing affecting the sensorrare
• Outdated or faulty control unit software, where the manufacturer has issued a fixrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data. Note any other motor, inverter or communication codes, and check for related manufacturer service bulletins.
2. Follow the manufacturer's high-voltage safety procedure. Only suitably trained people should work on or near orange high-voltage components.
3. Visually inspect the sensor harness and connectors at the motor and inverter for chafing, water ingress, corrosion, bent pins and poor locking.
4. Check for damage or oil or coolant contamination around the motor housing and sensor connector.
5. With the system safely isolated, test the sensor circuit wiring for continuity, shorts and resistance to the manufacturer's specification.
6. Measure the sensor coil resistances against the specification for the model.
7. Check the sensor signal with a suitable scope or live data while the motor turns, looking for dropouts, noise or an implausible waveform.
8. Check the control unit software version against current manufacturer information, and if it is the suspect, test with known-good wiring and sensor before replacing the unit.

How to fix

• Repair or replace damaged wiring, and clean or replace corroded or damaged connectors and terminals.
• Replace the motor position sensor, or the motor assembly if the sensor is not serviceable separately, and carry out any required position learning or adaptation.
• Restore the harness routing, shielding and earth connections to the original standard.
• Replace or repair the inverter or motor control unit only after wiring and sensor faults are ruled out.
• Update the control unit software if the manufacturer lists an outdated calibration as the cause.
• Clear the code after repair and road test to confirm it does not return.

Can I keep driving?

Nearby codes

• P0A44GenericDrive Motor A Position Sensor Circuit Overspeed
• P0A46GenericDrive Motor B Position Sensor Circuit Range/Performance