P0CBC

What it means

P0CBC means the control unit has found a fault in the circuit of the coolant temperature sensor for drive motor A, the traction motor on a hybrid or electric vehicle. The control module saw a sensor signal outside the expected range, or one that did not make sense against other temperature readings. Without a trusted motor coolant temperature, it cannot protect the motor properly, so it may limit power. The exact sensor location and the way the cooling loop is arranged depend on the model.

Symptoms

• Warning lamp on the dashboard, possibly with a hybrid or EV system message
• Reduced power or limp-home mode
• Reduced regenerative braking or limited charging
• Cooling fan or coolant pump running constantly or at odd times
• Temperature gauge or drive system temperature reading missing or implausible
• Car refusing to enter ready mode on some models

Possible causes

• Damaged wiring, chafing or corrosion in the sensor circuit (open circuit, short to ground or short to supply)likely
• Loose, corroded or contaminated sensor connector or control module connectorlikely
• Faulty drive motor A coolant temperature sensorlikely
• Coolant leak or contamination around the sensor or connectorpossible
• Low coolant level or air in the motor cooling loop giving implausible readingspossible
• Fault in the motor control module or inverter control unit, including software issues where the manufacturer has a known updaterare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, and note whether other motor, inverter or cooling codes are present
2. Check the coolant level and condition in the drive system cooling loop, and look for leaks, following the manufacturer's procedure for that model
3. Visually inspect the sensor, its wiring and connectors for damage, chafing, water ingress, corrosion or coolant contamination
4. Compare the live motor coolant temperature with other coolant temperature readings on a cold car; they should be close after a long soak
5. Unplug the sensor and measure its resistance against the manufacturer's temperature table, then check the reading changes smoothly as it warms
6. Check the reference voltage, signal and ground at the sensor connector, and test the wiring for continuity and shorts back to the control module
7. Check the cooling pump and fan operation, as a cooling fault can give a real over-temperature reading
8. Check for applicable service bulletins or software updates for the model. High-voltage systems must only be worked on by suitably trained and equipped technicians

How to fix

• Repair or replace damaged wiring and fix any short or open circuit found
• Clean, reseat or replace corroded or damaged connectors and terminals
• Replace the drive motor A coolant temperature sensor if its readings are out of specification
• Fix any coolant leak, then refill and bleed the cooling loop to the manufacturer's procedure
• Repair or replace a faulty coolant pump or fan if it is contributing to the fault
• Update the control module software only if a known fault is confirmed for that model, or replace the module if it is proven faulty

Can I keep driving?

Nearby codes

• P0CBBGenericHybrid/EV Battery Temperature Sensor P Circuit Intermittent/Erratic
• P0CBDGenericDrive Motor A Coolant Temperature Sensor Circuit Range/Performance