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How to Test the Temperature Sensor with a Multimeter

Model: (Various brands) Various
Part: Engine coolant temperature sensor

Video tutorial

The engine coolant temperature sensor (ECT) monitors the engine temperature and sends the data to the ECU, which uses it to manage injection, timing, and the fan. A faulty sensor causes temperature fluctuations, the fan not starting, or the warning light to illuminate.

To test it with a multimeter: locate the sensor (usually on the cylinder head, near the thermostat or coolant hoses), disconnect the electrical connector and set the multimeter to resistance measurement (Ohm). Connect the probes to the sensor terminals (polarity does not matter) and read the value.

Compare it with the specifications in the manual for ambient temperature. For a more accurate check, immerse the sensor tip in water at different temperatures (without wetting the connectors) and compare the values with the table in the manual.

If the value is within range, the sensor is good; if it is infinite (open circuit), it is faulty; if it is close to zero, it is short-circuited; if it is out of range, it is defective. Always work with the engine off and cold.

A good multimeter can be found on AliExpress with code 1005013396897652 for €26.69, with free shipping.


Posted on 1 November 2026 by ScegliAuto


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