Engine overheat — critical coolant temperature
The red thermometer icon fires when coolant temperature exceeds the critical threshold (usually 110–115 °C). Continued driving risks head-gasket damage, warped cylinder heads and a full engine rebuild.
What this indicator means
The Engine Coolant Temperature sensor (ECT) sends a live signal to the ECU. When the value goes out of range, the system switches on the indicator and can drop the engine into limp mode with forced power reduction. Normal operating range: 85–105 °C.
Common causes
- Low coolant level (leak in radiator, hoses or water pump)
- Thermostat stuck in closed position
- Radiator fan not running (fuse, relay, sensor)
- Clogged radiator (fluff, dirt, scale)
- Water pump not circulating fluid (worn bearing, sheared impeller)
- Blown head gasket (combustion gases entering the expansion tank)
What to do as a driver
Pull over as soon as possible in a safe location. Do NOT open the expansion-tank cap on a hot engine — you will be scalded. Let the engine cool for 20–30 minutes, then check fluid level. If you must limp on, set the heater to max (extra radiator), reduce speed, use hazard lights.
Safety
Maximally critical: further driving = engine rebuild. Call a tow truck if overheat recurs after cooling down.
Related DTC codes
- P0217
- P0128
- P0480