What it means
The vehicle hybrid control module detects a circuit high 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 uses its signal to assess cooling needs; this code sets when the signal is abnormally high, which can result from an open sensor circuit or a signal wire shorted to battery voltage.
Common causes
Most likely first.
- Signal wire shorted to B+
- Open sensor
- 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
- Review freeze-frame data and live sensor B temperature, comparing it with other coolant readings and ambient temperature to see whether it is implausibly high.
- Inspect sensor B's connector and harness for corrosion, loose terminals, broken wires, or insulation damage that could expose the signal wire to battery voltage.
- With the vehicle powered down as specified by the manufacturer, check sensor B connector pins for corrosion or poor contact.
- Use the wiring diagram to test the sensor B signal circuit for an open and for an unintended connection to battery voltage.
- Test sensor B and its reference and ground circuits against the manufacturer's specification to determine whether the sensor itself is open.
Common fixes
- Clean and secure corroded or loose sensor B connector terminals.
- Repair an open wire or a signal wire shorted to battery voltage in the sensor B circuit.
- Replace sensor B if it fails testing.
- Clear the code and confirm sensor B reports a plausible temperature.
Can I keep driving?
Reduced hybrid or electric power may make acceleration unpredictable, and the module may not assess power-electronics cooling correctly. Avoid hard acceleration 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.