Thursday, February 2, 2012

How To Test An Engine Coolant Temperature Sensor

     Do you think you have a bad engine coolant temperature sensor or ECT? Often times thay will go bad with no diagnostic trouble code to point you in that direction. Testing an ECT is easy and a great way to start troubleshooting your vehicle if you are having driveability issues.
     The ECT sends a signal to the Powertrain Control Module, PCM, so it can measure the temperature of the engine coolant. The sensor's element is submerged directly into the vehicle's coolant. They are usually located near the thermostat housing on most vehicles.
     To test an ECT you will need a multimeter. Any type or brand will do, even the cheapo $5 ones at Harbor Freight. You don't need to remove the sensor from the vehicle, just the electrical connector. Make sure the car is off!
     Now set the multimeter to ohms and measure the resistance across the two terminals on the sensor. If the sensor has 4 terminals then you should measure across 1-4 and then 2-3. The resistance should read between 700 and 1000 ohms for most vehicles with the coolant at operating temperature. If the car is cool, say around room temp, the resistance should be much higher, between 7000 and 13000 ohms. If resistance is not within spec, you should replace the sensor.
     So there you have it, testing an ECT made easy. ECT's are usually very cheap but can affect a lot of your vehicle's systems causing driveability issues. They are very simple to test and replace usually without loss of any coolant at all. Do not replace it when the vehicle is hot, let it cool down first. Good luck with your repair and diagnosis and if unsure about a procedure, always ask. Leave a comment here if you like.

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