Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Engine Coolant Temperature Sensor
Engine Coolant Temperature (ECT) sensor is a thermistor device in which resistance changes with temperature. Electrical resistance of a thermistor decreases as temperature increases, and increases as temperature decreases. Varying resistance affects voltage drop across sensor terminals and provides electrical signals to PCM corresponding to temperature. Thermistor type sensors are considered passive sensors. A passive sensor is connected to a voltage divider network so that varying resistance of passive sensor causes a variation in total current flow. Voltage that is dropped across a fixed resistor in a series with sensor resistor determines voltage signal at PCM. This voltage signal is equal to reference voltage minus voltage drop across fixed resistor. ECT measures temperature of engine coolant and is threaded into an engine coolant passage. ECT sensor is similar in construction to IAT sensor.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.