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
The engine coolant temperature sensor measure the temperature of the engine coolant. The temperature of the engine coolant is required so that the Engine Control Module (ECM) can regulate e.g.:
- injection period
- idling speed
- engine cooling fan
- ignition advance
- engagement and disengagement of the A/C compressor
- electric coolant pump
- electric thermostat
- automatic start/stop of engine
The sensor is a Negative Temperature Coefficient (NTC) type and is supplied with power from the control module (signal) and is grounded in the control module.
The resistance in the sensor changes depending on the temperature of the coolant. For information about electrical connection, see wiring diagram. For sensor characteristics and normal values, see signal specification and component specification.
The engine coolant temperature sensor can be diagnosed by the Engine Control Module (ECM) and the sensor value can be read off.
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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.