U0630Lost Communication With Engine Coolant Temperature Sensor 4
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Engines with split or multi-zone cooling may measure coolant temperature at more than three points, and a sensor that sends its value as a digital message instead of a resistance can be checked for silence. U0630 means the engine controller no longer receives such messages from coolant temperature sensor 4. No manufacturer documents U0630 publicly, and where sensor 4 sits is not standardised. Since 2021 CARB requires an approved monitoring plan when an engine judges its operating temperature from sensors placed in several distinct coolant loops, so a lost sensor counts as an emission fault. Such a bus sensor has just three wires (supply, ground, data), and those plus the connector are the first suspects. The controller then works with a substitute value, and the cooling strategy may become more conservative.
- What you may notice
- Check engine light
- Cooling fan may run more than usual
- Likely causes
- LikelyData, supply or ground wire to sensor 4 open or shorted
- PossibleCorroded or loose sensor connector
- PossibleSensor electronics failed
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €30 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.