P0C56

What it means

P0C56 is a generic hybrid/electric vehicle code. The control unit has found the signal from drive motor 'B' position sensor circuit 'A' (usually a resolver or similar rotor position sensor) to be out of range or implausible. It compares the reported rotor position and speed with expected values, or with other motor and system data, and the two do not agree. Exact sensor type, circuit naming and setting criteria vary by model, so check the manufacturer's data.

Symptoms

• Hybrid or EV system warning light and general fault lamp on
• Reduced power or limp-home mode
• Rough, jerky or hesitant drive-away
• Engine starting or stopping unexpectedly (hybrids), or loss of electric drive
• Vehicle will not enter Ready mode or shuts down while driving

Possible causes

• Damaged, corroded or loose wiring or connector on the motor position sensor circuitlikely
• Faulty drive motor position sensor (resolver or equivalent)likely
• Electrical interference or shorting to nearby high-current cabling due to chafed or damaged shieldingpossible
• Sensor misaligned or mounting disturbed after motor or gearbox workpossible
• Fault in the motor control unit or inverter that processes the sensor signalpossible
• Internal motor or bearing damage affecting rotor position readingrare

How to diagnose

1. Read all stored and pending codes and freeze frame data, noting speed, load and temperature when the fault set, and check for other motor, inverter or resolver codes.
2. Check for technical service bulletins and software updates for the model, as some applications have known causes.
3. Following the manufacturer's high-voltage safety procedure (only by a suitably trained technician), visually inspect the sensor wiring, connectors and shielding for chafing, water ingress, corrosion and pin damage.
4. Check the connector pins for tension and the harness for damage near the motor, brackets and moving parts.
5. Use live data to compare motor position and speed readings with other motor and vehicle speed data, and watch for dropouts when the harness is gently moved.
6. Test the sensor circuit resistance, continuity and shorts to power or earth against manufacturer specifications.
7. Check the sensor and its mounting for damage or misalignment, especially if recent work has been done on the motor or transmission.
8. If the wiring and sensor test good, check the inverter or motor control unit power, earths and communication before considering replacement.

How to fix

• Repair or replace damaged wiring, connectors or shielding on the position sensor circuit.
• Clean and secure corroded or loose connections, and seal against moisture ingress.
• Replace the faulty motor position sensor, or the motor assembly if the sensor is not serviceable separately, and carry out any required position learning or setup.
• Refit or realign the sensor correctly if it has been disturbed, following the manufacturer's procedure.
• Replace or reprogram the inverter or motor control unit only after confirming the fault, and apply any manufacturer calibration update if an outdated calibration is a known cause.

Can I keep driving?

Nearby codes

• P0C55GenericDrive Motor B Position Sensor Circuit A
• P0C57GenericDrive Motor B Position Sensor Circuit A Low