P0CDB

What it means

P0CDB means the control unit for the hybrid or electric drive motor 'A' has found the signal from the motor position sensor (usually a resolver or similar rotor angle sensor) on circuit C to be out of its expected range or implausible. The control unit compares the signal with expected values, other sensor circuits or the calculated motor speed and angle, and the mismatch sets the code. Which signal 'circuit C' refers to (for example a sine, cosine or excitation line) depends on the vehicle, so check the manufacturer's data.

Symptoms

• Warning lights on, such as the hybrid or EV system fault light or the malfunction indicator lamp
• Reduced power or limp mode
• Rough, jerky or hesitant drive-off or acceleration
• Vehicle will not enter Ready mode or will not move
• Engine starting or stopping unexpectedly on a hybrid
• Reduced regenerative braking

Possible causes

• Damaged, chafed or corroded wiring or connector between the position sensor and the motor control unitlikely
• Faulty motor position sensor (resolver) or sensor out of alignment or looselikely
• Electrical interference or signal noise from damaged shielding or a poor earth connectionpossible
• Water or coolant ingress or contamination at the motor or sensor connectorpossible
• Faulty inverter or motor control unit, or its sensor interface circuitpossible
• Mechanical damage to the motor, such as a bearing or rotor fault affecting the sensor signalrare
• Outdated or faulty control unit software where the manufacturer has issued a known fixrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting any other motor, inverter or sensor codes and the conditions when the fault set.
2. Check for manufacturer service bulletins and known software issues for the model and the code.
3. Follow the manufacturer's high-voltage safety procedure; only a suitably trained technician should work on high-voltage components or open the system.
4. Visually inspect the position sensor wiring, shielding and connectors at the motor and the inverter for chafing, corrosion, moisture, bent pins or loose fit.
5. Check live data for motor speed and angle while the car is stationary and while it is moving, looking for dropouts, spikes or disagreement between sensor signals.
6. With the system safely isolated, test the sensor circuit for continuity, short circuits to earth or voltage, and the sensor coil resistance against the manufacturer's specification.
7. Check the sensor signal on a scope if the manufacturer's procedure allows, looking for amplitude, shape and noise problems.
8. Check the motor housing and connector area for coolant or water ingress, and the earth and shield connections.

How to fix

• Repair or replace damaged wiring, shielding or connectors in the position sensor circuit.
• Replace the motor position sensor, or the motor assembly where the sensor is not serviceable separately, and carry out any required sensor learn or calibration procedure.
• Dry out and clean contaminated connectors, fix the source of water or coolant ingress and replace any corroded terminals.
• Repair loose or corroded earth and shield connections to remove signal noise.
• Replace or repair the inverter or motor control unit only after the wiring and sensor have been proven good.
• Update the control unit software if the manufacturer lists it as a fix for this fault.

Can I keep driving?

Nearby codes

• P0CDAGenericDrive Motor A Position Sensor Circuit C
• P0CDCGenericDrive Motor A Position Sensor Circuit C Low