Cooling
Coolant Temperature Sensor (ECT)
The ECT sensor tells the ECU how hot the engine is so it can manage fuel, fans and gauges.
Free guide
Advertisement
Cooling system flow
Interactive — tap a partTap a part to see how it fits in the system.
What it does
- Measures engine coolant temperature
- Feeds the gauge and ECU strategy
- Controls the cooling fan stages
When it fails
- P0115–P0118 codes
- Engine runs rich (thinks it is cold)
- Fan runs constantly
- Gauge reads wrong
How to diagnose
- Compare live temperature to a thermometer
- Measure sensor resistance at cold/warm
- Check wiring and connector
Maintenance
- Replace with the correct temperature curve for the engine
Use the diagnosis order. When a part fails, confirm each hypothesis with measurements before replacing anything — codes and symptoms overlap.
Related part
Thermostat
A small valve that keeps the engine at operating temperature by controlling coolant flow to the radiator.