What it means
The HV battery temperature sensor M reports a circuit high fault. Cell-group temperature monitoring impaired on this channel.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Sensor M measures temperature at its assigned area of the high-voltage battery, and the control module uses it to manage battery protection, power, and charging. This code sets when the M circuit signal is higher than expected, often because the signal wire is shorted to battery voltage or the sensor circuit is open.
Common causes
Most likely first.
- Signal wire shorted to B+
- Open sensor
- Connector pins corroded - high contact resistance
Symptoms
- EV/hybrid system warning light on
- Reduced power output or limp mode
- Charging may fail or be slowed
- Reduced electric range
How to diagnose it
- Save freeze-frame data and compare Sensor M's reported temperature with other battery sensors; a fixed or implausible reading can point to the high-signal fault.
- With the vehicle safely powered down per the manufacturer's procedure, inspect Sensor M's connector and wiring for loose pins, corrosion, breaks, or contact with a power feed.
- Check the connector fit and pin condition, since corrosion or a loose terminal can interrupt the sensor circuit.
- Test the Sensor M signal wire for an open circuit and for a short to voltage, following the manufacturer's procedure.
- Test the M sensor and verify the control module input only after checking the connector and harness.
Common fixes
- Reseat the Sensor M connector and clean or repair corroded terminals.
- Repair an open or damaged Sensor M wire or insulation shorted to voltage.
- Replace Sensor M if it is open or fails the manufacturer's test.
- Repair the module connection or replace the control module only if its input is confirmed faulty.
Can I keep driving?
The vehicle may restrict power or charging because it cannot trust Sensor M's battery temperature reading. Avoid long trips or demanding acceleration, and follow any stop or service warnings shown by the vehicle.
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.