P0A55
Drive Motor B Current Sensor Circuit.
- Generic
- Powertrain
- Generic code
- High severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- A
- AreaHybrid propulsion
- 55
- FaultThe specific fault in that area
What it means
P0A55 is the generic code for a fault in the drive motor 'B' current sensor circuit on a hybrid or electric vehicle. The motor control or inverter control unit monitors the sensor signal and set the code because it was missing, out of range, implausible against other motor data, or the circuit was open or shorted. Which motor is 'B' and how the sensor is built depends on the model.
Symptoms
- Hybrid or EV system warning light, often with the main warning light
- Reduced power or the car going into a limp mode
- Vehicle will not enter ready mode or will not move
- Rough or jerky drive or poor acceleration
- Engine running more than normal on a hybrid because motor assist is limited
- Intermittent loss of drive that may clear after a restart
Possible causes
- Wiring or connector fault in the current sensor circuit (chafing, corrosion, loose pin, water ingress)likely
- Faulty drive motor current sensor, which is often built into the inverter or motor power modulelikely
- Fault inside the inverter or motor control unit affecting the sensor supply or signalpossible
- Low or unstable 12 V supply or poor earth to the control unitpossible
- Damaged high voltage phase cable or terminal causing abnormal current readingsrare
- Outdated or faulty control unit software where the manufacturer has issued a fix for this faultrare
How to diagnose
- Read all stored and pending codes and note any other motor, inverter, resolver or high voltage codes that point to a common cause.
- Review freeze frame data to see speed, load, temperature and system state when the fault set, then check whether it returns after clearing.
- Check the 12 V battery condition and charging voltage, as low voltage can upset the control units and set sensor faults.
- Visually inspect the sensor and inverter wiring and connectors for chafing, corrosion, moisture, heat damage and bent or pushed-back pins. Only a technician trained in high voltage systems should go near orange high voltage components.
- Look at live data for the motor current readings with the car at rest and compare them with the expected near-zero values and with the other motor or phases, where the model provides this.
- Gently wiggle test the harness with live data on to find an intermittent fault.
- Following the manufacturer's procedure with the high voltage system isolated by a trained technician, test the sensor circuit for supply, signal and earth, plus continuity and short circuits.
- Check for service information or software updates relating to this code for the specific model.
How to fix
- Repair or replace damaged wiring, terminals or connectors in the sensor circuit.
- Replace the current sensor or the assembly that contains it, as the manufacturer specifies.
- Repair or replace the inverter or motor control unit if testing shows an internal fault, then carry out any required setup procedure.
- Restore a healthy 12 V supply by charging or replacing the battery and repairing poor earth connections.
- Repair any damaged high voltage cable or terminal, using a trained technician and the correct isolation procedure.
- Update the control unit software only if the manufacturer lists an update for this fault.
Can I keep driving?
High severity
Avoid driving if the car is in limp mode, has lost drive, or the hybrid or EV warning is on, as power can drop suddenly. Have it checked by a technician trained in high voltage systems as soon as possible.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.