U063BLost Communication With Coolant Bypass Valve Actuator A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Rotary coolant valves are often moved by a smart actuator that takes its target angle over LIN and reports back. U063B covers the case where actuator A no longer replies. Mercedes-Benz uses it in the drivetrain controller N127 (PTCU, CPC3) for the control valve of the high-temperature circuit; bulletin LI20.00-P-076708 for the GLC 254 and the facelifted GLE 167 (model year 2024) lists U063B00 and U063B87 (message missing) together with codes for fan 1, coolant pumps and an exhaust flap on the same LIN line. The check engine lamp comes on, a coolant service message appears and the radiator fan runs flat out. For the GLC with PTCU version 22A the cure is new software; otherwise connectors and LIN wiring are inspected. Electrical faults of the valve drive itself are P0E75 to P0E7A.
- What you may notice
- Check engine light with coolant service message
- Radiator fan permanently running at full speed and noisy
- Further LIN codes (fan, coolant pumps, exhaust flap) stored together
- Likely causes
- LikelyOutdated drivetrain controller software (Mercedes PTCU version 22A)
- PossibleDamaged, chafed or corroded LIN wiring or intermediate connectors
- PossibleElectronics in valve actuator A failed
- RareMissing supply voltage or ground at the actuator
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.