What it means
The hybrid control module detects an out-of-range signal from the temperature sensor of the inverter/motor electronics coolant loop. This sensor protects power electronics from overheating.
At a glance
- Usually lights the check-engine light
How it works
The motor electronics coolant temperature sensor reports the temperature of the coolant that removes heat from the inverter and related hybrid power electronics. The hybrid control module monitors the sensor signal for an electrical value outside its acceptable range; that can prevent it from reliably assessing electronics temperature.
Common causes
Most likely first.
- Temperature sensor failed
- Wiring or connector fault
Symptoms
- Hybrid system or check-engine warning light on
- Possible reduced hybrid power
How to diagnose it
- Use a hybrid-capable scan tool to record freeze-frame data and compare the motor electronics coolant temperature reading with other available temperature readings when the vehicle is cold.
- Inspect the coolant temperature sensor connector and nearby wiring for looseness, corrosion, damaged insulation, or signs of coolant intrusion.
- Check the motor electronics coolant level and look for leaks or evidence that the loop may not be circulating properly.
- With the vehicle made safe according to the manufacturer's high-voltage procedures, test the sensor circuit and ground for opens, shorts, or poor connections.
- Compare the sensor's measured response with the manufacturer's specification to determine whether the sensor itself is faulty.
Common fixes
- Reconnect and secure a loose sensor connector.
- Repair damaged or corroded wiring or connector terminals.
- Replace the motor electronics coolant temperature sensor if its signal is outside specification.
- Restore the coolant level and repair any leak found in the motor electronics cooling loop.
Can I keep driving?
If the warning is on but the vehicle drives normally, limit driving and avoid heavy acceleration or steep climbs because the module may not be able to judge power-electronics temperature. Stop if hybrid power drops or an overheating warning appears; continued operation could damage the inverter or motor electronics.
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.