P0CB5

What it means

P0CB5 means the hybrid or EV battery control unit saw the signal from battery temperature sensor 'O' sit higher than its expected range. On a typical thermistor circuit this usually points to an open circuit, a short to voltage, or a failed sensor. Which physical sensor 'O' refers to depends on the model and pack design, so check the manufacturer's data for its location.

Symptoms

• Hybrid or EV system warning light on the dashboard, often with the main warning light
• Reduced power or limp mode
• Reduced regenerative braking or charging speed, or charging refused
• Cooling fans for the battery running harder than expected, or not running at all
• Reduced electric-only range or the engine running more often on a hybrid
• Car in rare cases will not enter ready mode

Possible causes

• Open circuit or poor connection in the sensor wiring or connector, including corrosion or a loose terminallikely
• Faulty battery temperature sensor (internal open circuit)likely
• Damaged sensor harness inside the battery pack, or short to a voltage supply in the wiringpossible
• Moisture or coolant ingress at the sensor or connectorpossible
• Fault in the battery monitoring unit or control unit input circuitrare
• Outdated control unit software that misreads the sensor, where the manufacturer has documented thisrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting pack temperature, state of charge and vehicle state when the code set.
2. Check for other battery temperature, voltage or communication codes, since a shared fault such as a power supply or ground problem points away from this single sensor.
3. Look at live data for all battery temperature sensors. Compare sensor O with the others and with ambient temperature. A reading stuck at an extreme, such as very cold or at the limit, suggests an open circuit.
4. Follow the manufacturer's high-voltage isolation procedure. Only a suitably trained technician should work on the high-voltage system.
5. Inspect the sensor connector and harness for damage, corrosion, pushed-out pins, water ingress or chafing, using the model's wiring diagram to locate sensor O.
6. Measure sensor resistance and compare it with the temperature-resistance specification, then check the reference voltage, signal wire continuity and any short to voltage or ground.
7. Wiggle-test the harness and connector while watching live data to find intermittent faults.
8. Check for manufacturer software updates or technical bulletins covering this code on the specific model.

How to fix

• Repair or replace damaged wiring, terminals or connectors, and seal out any moisture.
• Replace the faulty temperature sensor or the sensor harness, following the manufacturer's procedure, which may mean opening the battery pack or replacing a pack section.
• Replace the battery monitoring unit or control unit only once the sensor, wiring and supply have been proven good.
• Update the control unit calibration only if the manufacturer lists an outdated calibration as a known cause.
• Clear the code, then road test and recheck live data to confirm the sensor reads plausibly and the code stays cleared.

Can I keep driving?

Nearby codes

• P0CB4GenericHybrid/EV Battery Temperature Sensor O Circuit Low
• P0CB6GenericHybrid/EV Battery Temperature Sensor O Circuit Intermittent/Erratic