What it means
The motor electronics coolant temperature sensor reading is implausible relative to other thermal models or coolant flow estimates.
At a glance
- Usually lights the check-engine light
How it works
The motor electronics coolant temperature sensor measures the temperature in the cooling loop for the inverter and other hybrid power electronics. The hybrid control module sets this range/performance code when the reading is electrically plausible but does not agree with expected temperature changes, thermal models, or estimated coolant flow.
Common causes
Most likely first.
- Sensor drift
- Low coolant flow
- Sensor element aged beyond calibration window
Symptoms
- Hybrid system or check-engine warning light on
- Possible reduced hybrid power
How to diagnose it
- Record freeze-frame data and compare the sensor reading with ambient and other available temperatures after the vehicle has cooled; an implausible starting difference can point to sensor drift.
- Watch live motor electronics coolant temperature while the vehicle warms up and compare its response with the manufacturer's expected behavior.
- Check the coolant level, inspect for leaks, and confirm that the motor electronics loop shows evidence of circulation.
- Inspect the sensor connector and harness for corrosion, loose terminals, or damage that could distort the reading.
- Test the sensor response and the cooling loop's flow-related components against the manufacturer's specification before replacing parts.
Common fixes
- Correct a low coolant level and repair any leak.
- Clean or repair a loose, damaged, or corroded sensor connection.
- Restore restricted or weak coolant circulation in the motor electronics loop.
- Replace the temperature sensor if its readings drift outside the manufacturer's specification.
Can I keep driving?
Keep driving to a minimum and avoid high loads, since an inaccurate temperature reading or poor coolant flow can leave the inverter insufficiently protected. Stop if the vehicle reduces hybrid power or displays an overheating warning.
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.