What it means
The vehicle hybrid control module detects a circuit low fault on the coolant temperature sensor B that monitors the power electronics cooling loop.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Sensor B measures coolant temperature in the hybrid and EV power-electronics cooling loop. The hybrid control module watches its signal to assess cooling needs; this code sets when the signal is abnormally low, as can happen with a short to ground or a failed sensor.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- Connector pins corroded - high contact resistance
Symptoms
- Hybrid-system or powertrain warning light
- Reduced hybrid or electric drive power
- Cooling-system warning
How to diagnose it
- Check freeze-frame data and live readings for sensor B, comparing its temperature with other available coolant readings when the vehicle is cold and warmed up.
- Inspect sensor B's connector and nearby harness for corrosion, moisture, damaged insulation, or a signal wire touching ground.
- With the vehicle powered down as specified by the manufacturer, check the sensor B connector terminals for corrosion, looseness, or poor contact.
- Use the wiring diagram to test sensor B's signal circuit for an unintended connection to ground and check its reference and ground circuits.
- Test sensor B against the manufacturer's specification and compare the result with the harness-side signal to distinguish a failed sensor from a wiring fault.
Common fixes
- Clean and secure corroded or loose sensor B connector terminals.
- Repair a signal wire shorted to ground or other damaged wiring in the sensor B circuit.
- Replace a failed sensor B.
- Clear the code and confirm sensor B readings are plausible during operation.
Can I keep driving?
Reduced electric or hybrid power may limit acceleration, and the module may not be able to judge power-electronics cooling correctly. Avoid demanding driving and stop safely if a cooling warning or overheating indication appears.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.