What it means
The HV battery temperature sensor O reports a circuit low 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 O is one of the temperature sensors used to monitor a section of the high-voltage battery. The battery control module checks its signal for a voltage below the permitted range, which can indicate a grounded signal wire or a shorted sensor and leaves that cell group’s temperature uncertain.
Common causes
Most likely first.
- Signal wire shorted to ground
- Internal sensor short
- 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
- Use a scan tool to record freeze-frame data and compare Sensor O’s reading with other battery temperature sensors when the vehicle is cold and temperatures should be similar.
- With the vehicle powered down according to the manufacturer’s high-voltage safety procedure, inspect Sensor O’s connector and harness for corrosion, damaged insulation, or a signal wire touching ground.
- Check whether the fault returns and whether Sensor O’s live reading remains implausibly low compared with nearby sensors.
- Test Sensor O’s signal circuit for a short to ground and check connector contact condition using the manufacturer’s wiring information.
- If the wiring and terminals are sound, test Sensor O against the manufacturer’s specification and replace the sensor if it is internally shorted.
Common fixes
- Clean or repair corroded Sensor O connector terminals and ensure the connector is fully seated.
- Repair the Sensor O signal wire where it is shorted to ground or damaged.
- Replace Sensor O if it fails the manufacturer’s sensor test.
Can I keep driving?
Limit driving if the vehicle has reduced power, and do not rely on normal charging or electric range while Sensor O’s battery section temperature is unknown. Stop safely if a high-voltage or battery warning appears or power drops sharply, since the vehicle may restrict operation to protect the battery.
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.