Faulty traction battery temperature sensor D or E giving an inaccurate reading; Damaged wiring, poor connection or corrosion at the sensor or battery management connector; Uneven battery cooling from a blocked intake, dirty filter or failing battery cooling fan; Localised cell or module fault causing a real temperature difference within the pack; Fault in the battery management unit or its sensing circuit; Outdated or faulty control unit software, where the manufacturer has issued a correction.

P0C71

Hybrid/EV Battery Temperature Sensor D/E Correlation.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
C: AreaHybrid propulsion
71: FaultThe specific fault in that area

What it means

P0C71 is a generic powertrain code meaning the control unit has found a correlation fault between two hybrid or EV traction battery temperature sensors (labelled D and E). The battery management system compares the readings from these sensors, and they differ by more than expected or do not track each other as they should. Sensor locations and the exact pairing depend on the vehicle and battery pack design.

Symptoms

Hybrid system or battery warning light on the dashboard
Reduced electric assist or reduced EV power
Cooling fan for the battery running louder or more often than normal
Reduced charging speed or charging limited
Poor fuel economy because the hybrid system is limiting battery use
Car enters limp mode or fails to ready in some cases

Possible causes

Faulty traction battery temperature sensor D or E giving an inaccurate readinglikely
Damaged wiring, poor connection or corrosion at the sensor or battery management connectorlikely
Uneven battery cooling from a blocked intake, dirty filter or failing battery cooling fanpossible
Localised cell or module fault causing a real temperature difference within the packpossible
Fault in the battery management unit or its sensing circuitrare
Outdated or faulty control unit software, where the manufacturer has issued a correctionrare

How to diagnose

Read all stored and pending codes and note the freeze frame data, including battery temperatures and ambient temperature.
Check for related codes covering other battery temperature sensors, cooling fan, or cell voltage faults, and deal with those first.
With the car fully cooled after standing, compare live temperature readings from all battery sensors; they should be close to each other and to ambient.
Inspect the battery cooling air intake, ducting and filter for blockage, debris or damage, where fitted.
Check the battery cooling fan operates and runs smoothly, using the scan tool's active test if the model supports it.
Inspect accessible wiring and connectors for damage, moisture or corrosion, following the manufacturer's high-voltage safety procedure.
Check resistance and wiring continuity of the suspect sensor circuit against manufacturer specifications, as values vary by model.
Check for manufacturer software updates or technical bulletins for this model.

How to fix

Replace the faulty temperature sensor or sensor harness section as per manufacturer procedure.
Repair or clean affected connectors and wiring.
Clear blockages and replace the cooling filter or faulty cooling fan.
Repair or replace the affected battery module or pack if a real thermal imbalance is confirmed.
Replace the battery management unit only after wiring and sensors are proven good.
Apply a manufacturer software update if a known fault in the calibration is identified.

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but power may be limited and the battery could be at risk if temperatures are genuinely uneven. Get it checked soon, and stop driving if a red hybrid warning appears or the car smells of burning or overheats.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.