U0636Lost Communication With Hybrid/EV Battery Pack Coolant Control Valve A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- Battery thermal loops use motor-driven valves to send coolant through the chiller, the heater or a bypass, or to link the battery loop with the drive unit circuit. Many of these valves have a small controller of their own: Hutchinson's rotary three-way valve for electric vehicles talks LIN, and Thomas offers its coolant valves with PWM, LIN or CAN control and an optional self-diagnosis. U0636 is stored when valve A stops replying to the battery or thermal controller. No manufacturer documents the code publicly. Valve A then holds its last or default position, so the pack may be cooled or heated too little; CARB treats such valves on hybrids as monitored thermal management outputs. P0CDF to P0CE3 cover the electrical control circuit of the same valve.
- What you may notice
- Battery or hybrid system warning
- Reduced fast-charging power or limited drive power when the battery is hot or cold
- Cabin heating or cooling behaving differently
- Likely causes
- LikelyLIN, supply or ground wire to valve A damaged
- PossibleCorroded or loose valve connector
- PossibleValve A actuator electronics failed
- RareThermal or battery controller software fault
- 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 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.