What it means
The ECM detects a intermittent/erratic 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 reports temperature to the vehicle control module, which checks that the signal remains stable and plausible. This code sets when the signal becomes intermittent or erratic, often because a connector or wire loses contact as the vehicle moves or warms up.
Common causes
Most likely first.
- Loose or damaged sensor connector
- Damaged wiring causing an intermittent connection
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 note whether the fault occurred during charging, driving, or a temperature change.
- Monitor sensor B live data for sudden jumps, dropouts, or implausible changes while the vehicle is safely stationary.
- With the vehicle powered down as specified by the manufacturer, inspect sensor B's connector for looseness, corrosion, or damage.
- Inspect accessible sensor B wiring for chafing or breaks, and check for signal dropouts using the manufacturer's procedure.
- Compare sensor and circuit behavior with the manufacturer's specification and repair the connection or wiring responsible for the interruption.
Common fixes
- Secure a loose sensor B connector and clean corroded terminals.
- Repair intermittent or damaged wiring in the sensor B circuit.
- Replace sensor B if its signal drops out with a sound connector and harness.
- Clear the code and confirm the reading remains stable during operation.
Can I keep driving?
An intermittent reading can cause reduced power or charging limits without warning. Avoid demanding driving if the hybrid system warning or reduced power appears, and stop if a battery temperature warning is displayed.
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.