U0629Lost Communication With A/C Refrigerant Temperature Sensor B
- Generic OBD-II code · Network
- How the car detects it
- A second refrigerant temperature point is typical where an electronic expansion valve meters flow, for instance at the evaporator or chiller outlet, so that superheat can be calculated from temperature and pressure. U0629 is logged when the controller stops getting answers from temperature sensor B over its serial link. A digital sensor can diagnose its own measuring element, so U0629 points to the transmission path or to a sensor that has gone completely silent, not to a merely implausible reading. When U0628 is stored as well, a combined pressure/temperature unit B or its line is the likely common cause. No manufacturer documents U0629 publicly. Often only one operating mode, such as battery chilling or heat pump, is lost. Analog circuit faults are P0EC1 to P0EC4.
- What you may notice
- Battery cooling or heat-pump mode unavailable
- Uneven or reduced A/C performance
- Likely causes
- LikelyLIN line or connector at temperature sensor B open, shorted or corroded
- PossibleCombined pressure/temperature unit B failed (often together with U0628)
- RareFuse or supply feed for sensor B open
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €450
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.