What it means
The ECM detects a high fault on the hybrid/ev electronics coolant temperature sensor a circuit. Reading cannot be used reliably for control.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The hybrid/EV electronics coolant temperature sensor A reports coolant temperature for high-voltage electronics cooling. The ECM monitors its signal, and this code sets when the circuit voltage or reported value is higher than expected, which makes the temperature reading unreliable.
Common causes
Most likely first.
- Signal wire shorted to B+
- Open sensor
- Connector pins corroded - high contact resistance
Symptoms
- Hybrid or EV system warning light on
- Reduced power or limited vehicle operation
- Cooling-system warning may appear
How to diagnose it
- Check freeze-frame data and live sensor A temperature for an implausibly high or fixed reading.
- With the vehicle powered down as directed by its service information, inspect sensor A, its connector, and nearby wiring for loose pins, corrosion, or damage.
- Check the sensor A signal wire for a short to battery voltage and inspect the harness for contact with powered wiring.
- Check the sensor connector terminals and ground reference for high resistance or an open connection.
- Test sensor A and its circuit against the manufacturer's specification to determine whether the sensor is open or the wiring is at fault.
Common fixes
- Repair a loose, corroded, or poorly connected sensor A connector.
- Repair the signal wire if it is shorted to voltage or open.
- Replace a faulty hybrid/EV electronics coolant temperature sensor A.
- Clear the code and verify that sensor A reports a plausible, stable temperature.
Can I keep driving?
If the hybrid/EV warning or reduced-power mode appears, avoid driving farther than needed to reach a safe place; the vehicle may not be able to manage electronics cooling correctly. Do not continue a long or demanding trip until the fault is checked, because an inaccurate temperature signal can compromise protection against overheating.
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.