What it means
The ECM detects a low fault on the hybrid/ev battery pack coolant temperature sensor b 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
Battery pack coolant temperature sensor B sends a signal to the vehicle control module so it can manage battery cooling and charging. This code sets when the signal is lower than expected, which can be caused by a signal wire shorted to ground or an internally shorted sensor.
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
- Save freeze-frame data and check sensor B live data to see whether the reported temperature or signal is unusually low or fixed.
- With the vehicle powered down as specified by the manufacturer, inspect sensor B's wiring for chafing or contact with ground and check its connector for corrosion.
- Check connector pins for poor contact and inspect the accessible harness for damage that could pull the signal low.
- Test the sensor B circuit for a short to ground and check the sensor using the manufacturer's procedure.
- Compare circuit and sensor measurements with the manufacturer's specification before replacing the sensor.
Common fixes
- Clean and secure corroded or loose sensor B connector terminals.
- Repair the sensor B signal wire if it is shorted to ground or damaged.
- Replace sensor B if testing confirms an internal short.
- Clear the code and verify that sensor B data is plausible.
Can I keep driving?
The vehicle may limit power or charging because it cannot reliably assess battery coolant temperature. Avoid hard acceleration if power is reduced, and stop if a battery temperature warning appears.
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.