What it means
The ECM detects a circuit high 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 battery-pack coolant temperature to the control module over a dedicated signal circuit. This high-circuit code sets when the module sees that signal above its expected electrical range, commonly because the circuit is open or shorted to battery voltage.
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
- Capture freeze-frame data and compare sensor C's live value with other pack temperature sensors for an implausibly high or fixed reading.
- Inspect sensor C's connector and harness for a disconnected plug, backed-out terminal, corrosion, or damage.
- Check the signal wire for an open circuit or short to battery voltage using the manufacturer's wiring information and safety procedure.
- Test the sensor itself for an open element and verify connector contact quality against the manufacturer's specification.
- If the circuit and sensor pass, check the module connector and its input circuit.
Common fixes
- Reconnect a loose sensor C connector and secure its harness.
- Repair an open or shorted-to-voltage section of the signal wire.
- Replace sensor C if it is open or fails the manufacturer's test.
- Repair poor terminals at the module connector if confirmed by testing.
Can I keep driving?
Avoid continued use if the vehicle limits power or will not charge, and have the circuit checked promptly. A falsely high or unavailable pack temperature reading can trigger further battery-use restrictions.
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.