The coolant temperature sensor (G62) is a cheap part behind several confusing symptoms — the ECU uses it for fuelling, so a bad one causes running problems, not just a wrong gauge.
Symptoms:
- Hard cold starts, rough cold running, poor economy as the ECU mis-fuels on a false temp reading.
- The temp gauge reading wrong or erratic, or the fan running constantly / never.
- A stored coolant-temp code (P0116–P0118).
The fix:
- Replace the G62 sensor — on VWs it's in the coolant flange; the plastic flange itself also cracks and leaks, so inspect it. Fit the updated sensor + retaining clip.
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