U0635Lost Communication With Hybrid/EV Battery Pack Coolant Temperature Sensor B
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Sensor B is the second battery coolant temperature point, commonly placed on the opposite side of the pack from sensor A so the controller can see how much heat the coolant picks up. U0635 means sensor B no longer delivers digital messages. No public manufacturer document uses the code. With sensor A still working the controller keeps one reference but loses the temperature difference across the pack, which it uses to size pump speed and chiller or heater demand. CARB's hybrid rules count such inputs among the battery thermal management parts that must be monitored, and also ask for a functional check of cooling where feasible. The analog circuit faults of the same sensor are P0CD5 to P0CD9. Check the wiring branch to B before replacing parts.
- What you may notice
- Battery or hybrid system warning
- Battery cooling runs more often or charging power is reduced
- Likely causes
- LikelyWiring branch to sensor B open, shorted or chafed
- PossibleMoisture or corrosion at the sensor B connector
- PossibleSensor B failed
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.