P0CAE

What it means

P0CAE means the hybrid or EV control system has found that one of the traction battery temperature sensors (identified by the number N) is giving a reading that is implausible or does not fit with the other sensors. The battery control unit compares each sensor against its neighbours, the coolant or intake air temperature and expected warm-up behaviour. It sets the code when the reading is stuck, drifts or differs too much, even though the circuit is not fully open or shorted. Sensor numbering and position vary by model and pack design.

Symptoms

• Hybrid or EV system warning light, or malfunction indicator lamp, on
• Reduced power or limited battery charge and discharge
• Battery cooling fan running loudly or constantly
• Reduced regenerative braking or lower electric-only range
• Hybrid system may not start or may fail to enter ready mode in some cases

Possible causes

• Faulty or drifting battery temperature sensor (internal fault giving a stuck or implausible value)likely
• Damaged wiring, corrosion or poor connection in the sensor circuit or pack connector causing high resistancelikely
• Sensor poorly seated or displaced from its position in the battery modulepossible
• Battery cooling system fault (blocked air duct, failed fan or poor coolant flow) causing a real temperature difference that looks like a sensor faultpossible
• Fault in the battery monitoring unit or its sensor input circuitrare
• Outdated battery control software where the manufacturer has issued a revision for sensor plausibility faultsrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting battery temperatures, ambient temperature and vehicle state when the code set.
2. Check for other battery temperature, cooling fan or battery monitoring codes, as these point to a common cause.
3. Compare live data for every battery temperature sensor after the car has been cooled down; they should read close to each other and to ambient. Identify which sensor N is the outlier.
4. Inspect the battery cooling air intake, ducts, filters and fan for blockage, debris or damage, and check coolant level and flow if liquid-cooled.
5. Follow the manufacturer's high-voltage safety procedure before touching any pack components, and only let suitably trained staff do this.
6. Inspect the sensor wiring and connectors for damage, moisture, corrosion or loose pins, and carry out a resistance and voltage drop test against the manufacturer's specification.
7. Check that the sensor is correctly fitted and compare its resistance against temperature with the specification for your model.
8. Check for available software updates or technical bulletins for your model before replacing major components.

How to fix

• Replace the faulty battery temperature sensor or sensor harness section, following the manufacturer's procedure.
• Repair or replace damaged wiring, and clean or replace corroded connectors.
• Refit or secure a displaced sensor correctly.
• Clear blockages and repair the battery cooling fan, ducts or coolant circuit as needed.
• Repair or replace the battery monitoring unit only after the sensor and wiring have been proven good.
• Apply an updated battery control software calibration if the manufacturer lists it as a fix for this fault.

Can I keep driving?

Nearby codes

• P0CADGenericHybrid/EV Battery Temperature Sensor N Circuit
• P0CAFGenericHybrid/EV Battery Temperature Sensor N Circuit Low