What it means
The ECM detects a circuit fault on the hybrid/ev battery pack coolant temperature sensor c 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
Sensor C reports coolant temperature for the hybrid or EV battery pack to the control module. The module monitors its electrical signal for a circuit fault and may limit battery use or charging if it cannot rely on that reading.
Common causes
Most likely first.
- Sensor failed
- Wiring or connector fault
- Pack cell imbalance approaching service threshold
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 C with other pack temperature readings and ambient temperature.
- With the vehicle powered down according to its high-voltage safety procedure, inspect sensor C's connector and harness for loose pins, corrosion, damage, or coolant intrusion.
- Check for related battery temperature, cooling, or cell-balance codes that could point to a wider pack issue.
- Test sensor C's wiring continuity, shorts, and connections to the module against the manufacturer's specification.
- Measure the sensor response across temperature changes and compare it with the manufacturer's specification before deciding whether the sensor or pack needs service.
Common fixes
- Reseat or repair a loose or damaged sensor C connector.
- Repair an open, shorted, or damaged section of sensor C wiring.
- Replace sensor C if its readings fail the manufacturer's test.
- Have the battery pack assessed if cell imbalance or a pack-level fault is also present.
Can I keep driving?
Avoid relying on electric power or charging if the vehicle has reduced power, refuses to charge, or displays a hybrid/EV warning; arrange prompt diagnosis. Continued use may cause the system to restrict operation further.
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.