P0CD6

What it means

P0CD6 means the hybrid or EV control system has found that the signal from battery pack coolant temperature sensor 'B' is not plausible. The reading may be stuck, drifting or out of step with other temperature sensors or with the expected behaviour of the cooling loop. The sensor circuit is not necessarily open or shorted, because a range/performance code is set when the value is wrong for the conditions. The exact sensor location and the meaning of 'B' depend on the model.

Symptoms

• Hybrid or EV system warning light or malfunction indicator on
• Reduced power or limited charging and regeneration (derate)
• Battery cooling fan or pump running constantly or not at all
• Reduced fast-charging speed or charging interrupted
• Reduced electric-only range or earlier engine starts on a hybrid
• Other battery temperature or coolant circuit codes stored alongside

Possible causes

• Faulty or drifting battery coolant temperature sensor Blikely
• Damaged wiring, chafed insulation or poor connector contact (corrosion, loose pins, moisture) in the sensor circuitlikely
• Low coolant level, air in the loop or poor coolant flow causing a genuine temperature mismatchpossible
• Failed battery coolant pump, valve or chiller giving real temperature readings that disagree with the other sensorspossible
• Sensor poorly seated or not in proper contact with the coolant or packpossible
• Fault in the battery management unit or its software calibrationrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting battery temperatures, coolant temperatures and vehicle state when the code set.
2. Check for related codes on other battery temperature sensors, the coolant pump or the cooling circuit, and for any applicable service bulletins for the model.
3. Inspect the battery coolant level and condition, and look for leaks, following the manufacturer's high-voltage safety procedure.
4. Visually inspect the sensor wiring and connectors for damage, corrosion, moisture and loose pins, without touching any high-voltage components unless qualified.
5. With the car cool and left to stand, compare live data from sensor B with the other pack temperature sensors and the ambient temperature; they should agree closely.
6. Watch sensor B live while the system warms up or cools down, looking for a stuck, jumping or slow-responding reading.
7. Check the sensor resistance and the circuit's supply, signal and ground against the manufacturer's specification.
8. Test the coolant pump and valves for operation and flow using the manufacturer's procedure, as this depends on the model.

How to fix

• Repair or replace damaged wiring and clean or replace faulty connectors in the sensor circuit.
• Replace sensor B if its readings are implausible or do not match the specification.
• Top up or refill the battery coolant with the correct specification and bleed air from the loop using the manufacturer's procedure.
• Repair or replace a faulty coolant pump, valve or other cooling component affecting flow.
• Update the battery management software only if the manufacturer lists an outdated calibration as a known cause for this code.
• Clear the code after repair and road test to confirm it does not return.

Can I keep driving?

Nearby codes

• P0CD5GenericHybrid/EV Battery Pack Coolant Temperature Sensor B Circuit
• P0CD7GenericHybrid/EV Battery Pack Coolant Temperature Sensor B Circuit Low