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U0630 Lost Communication With Engine Coolant Temperature Sensor 4

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Data, supply or ground wire to sensor 4 open or shorted
Corroded or loose sensor connector
Sensor electronics failed

Symptoms

  • Check engine light
  • Cooling fan may run more than usual

Repair estimate

DifficultyMediumDIY possible
Parts and labour€30–300
Time0.3–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

engine coolant temperature sensor 4vehicle bus wiring

Related codes

U0631P01E3P2182P0115P0128

References: law.cornell.edu, nxp.com, en.wikipedia.org.