Engine Coolant Temperature Sensor ️

This small sensor is a key signal maker for the engine control unit. It is needed to measure coolant heat so the car can adjust fuel mixture, ignition timing, radiator fan operation, and cold-start strategy. Without a correct reading, the engine may run too rich or too lean, especially during warm-up.

How It Works ⚙️

Inside the sensor is a thermistor. As coolant temperature rises, electrical resistance changes. The ECU reads this change as a temperature value and then commands the right injector pulse, idle speed, and fan switching. This helps prevent overheating and keeps emissions under control.

When It’s Failing

A bad sensor can cause hard starting, rough idle, higher fuel use, black smoke, weak acceleration, or the cooling fan running at the wrong time. In severe cases, incorrect data may contribute to overheating or engine knocking, and the check engine light may come on.

Compatible Models ✅

• QX50