P0CD8

What it means

P0CD8 means the control unit monitoring the hybrid or EV traction battery has seen the signal from battery pack coolant temperature sensor 'B' sit above its expected electrical range. This usually points to an open circuit, a short to voltage or a failed sensor, though the exact sensor location and the voltage thresholds depend on the model. With no trustworthy coolant temperature reading, the system may limit power or charging to protect the battery.

Symptoms

• Hybrid or EV system warning light on, possibly with a general malfunction lamp
• Reduced power or limp-home mode
• Reduced or restricted charging, or fast charging not available
• Battery cooling fan or pump running constantly or behaving oddly
• Poor electric-only range or reduced regenerative braking
• Other battery temperature or cooling circuit codes stored alongside

Possible causes

• Open circuit in the sensor wiring or a damaged sensor connector (broken wire, pushed-out pin, corrosion)likely
• Faulty battery pack coolant temperature sensor (internal open circuit or out-of-range output)likely
• Short to voltage or short to another circuit in the sensor signal wirepossible
• Poor or open sensor ground or reference supplypossible
• Moisture or coolant contamination in the connector or sensorpossible
• Fault inside the battery management unit or related control modulerare
• Outdated control unit software where the manufacturer has published a fix for this faultrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting any other battery temperature or cooling codes and the conditions when it set.
2. Using a scan tool, compare all battery temperature and coolant temperature readings. A sensor B reading stuck at an extreme value suggests an open circuit or sensor fault.
3. Check for manufacturer service bulletins and software updates for this model and code.
4. Only if you are trained for high-voltage systems, and with the high-voltage system isolated per the manufacturer's procedure, inspect the sensor harness and connector for damage, corrosion, moisture, chafing and loose pins.
5. With the system isolated, check the sensor's resistance against the manufacturer's temperature-to-resistance table for the model.
6. Check the sensor signal, reference and ground circuits for continuity, and for shorts to voltage or ground, using the wiring diagram.
7. Check the battery coolant level and that the cooling pump and fan operate, as the coolant system may be involved, although this code is an electrical fault.
8. If the wiring and sensor are good, have the battery management unit and its supply and ground tested following the manufacturer's procedure.

How to fix

• Repair or replace damaged wiring and clean or replace the faulty connector terminals.
• Replace the battery pack coolant temperature sensor if it is out of specification, using the correct procedure for the model.
• Repair the short to voltage or restore the missing ground or reference on the affected circuit.
• Dry out and seal the connector, and find and cure the source of moisture or coolant leakage.
• Update the control unit software if a published update addresses this fault, or replace the control module only after confirmed failure.
• Clear the code after repair and road test to confirm it does not return.

Can I keep driving?

Nearby codes

• P0CD7GenericHybrid/EV Battery Pack Coolant Temperature Sensor B Circuit Low
• P0CD9GenericHybrid/EV Battery Pack Coolant Temperature Sensor B Circuit Intermittent/Erratic