Engine Coolant Temperature Sensor Tests

Engine coolant temperature sensor circuit explained. The engine coolant temperature sensor is a variable resistor known as a thermistor. The PCM runs multiple tests on the sensor circuit to check for shorts and opens. I refer to a wiring diagram to create both faults while monitoring the sensor signal with a voltmeter and a scantool.
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The content of this video is available for informational and educational purposes only.
I cannot guarantee against improper use or unauthorized modifications of this information. MR. DIAGNOSTECH assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Use this information at your own risk. Any injury, damage, or loss that may result from improper use of these tools, equipment, or from the information contained in this video is the sole responsibility of the user and not MR. DIAGNOSTECH.

[@sheerwillsurvival2064]

Great video please keep them coming. Old school technician . Can you do some on pull up and pull down circuits and the difference in ground side switched and positive side switch. Little lost. Thanks

[@mekkibilal1372]

Great job thank you for the help

[@HS-fw2ed]

Very good job! Why doesn't the resistor inside the PCM create a voltage drop? Why, after that resistance, is the voltage still 5 volts?

[@MRDIAGNOSTECH]

When it is unplugged, the circuit is incomplete, and voltage is not used.

[@HS-fw2ed]

Thanks! 🙏

[@benjaminlevi7792]

Great information. Thank you 🙏🙏

[@patrickmoran6004]

Brilliant video.
Could you do one on the camshaft sensor.

[@abdussamaddhodhat4551]

Thank you sir very very good explanation

[@cristi9944]

A very precise and detailed explanation, thank you for deciding to share your experience. I am happy that there is still someone who also thinks about beginners. Thank you very much

[@MRDIAGNOSTECH]

You're very welcome!

[@Benefits-ix9jy]

@@MRDIAGNOSTECH yes good explanation.

[@Benefits-ix9jy]

i have a question. my car ONLY when the weather is freezing. on the initial start up in morning . the car does not high idle . it idle at 1000 aka it shakes . it suppose to idle at 1800 or more. the car has an electronic TB no IAC. i checked the coolant temp sensor value in morning it matches with the air temp sensor .what could be the problem in your opinion

[@Grunter123]

What a great explanation. Thanks for sharing.

[@sethusethuramalingam4735]

Useful

[@johnngo341]

You have a hell of a way of teaching. Thank you and keep up the good work

[@u.e.3769]

One of the best explanations Greetings from Germany😊

[@MRDIAGNOSTECH]

Thanks! 😃

[@geoff3172]

Great video, many thanks for posting

[@1231234abcab]

Good refresher course 👍🏽

[@MRDIAGNOSTECH]

Yes, thanks

[@patrickmoran6004]

The best explanation I've seen on UA-cam. Thank you.

[@journdiag7621]

Thank you for sharing your knowledge

[@Jemimah-b1y]

This is a great job here. Please, I need your opinion on a BMW i'm working on. The issue is, at high temp, even above 120°C, the fan will not start(that is abnormal). Once you unplug the ects, the fan will come up(normal, showing an open circuit). The confusing part is that, there is no DTC and all measurements are ok. What is your take on this?

[@MRDIAGNOSTECH]

@@Jemimah-b1y I would do a voltage drop test from the sensor signal to DME and from the sensor ground to a known good ground. It might have unwanted resistance on the circuit.

[@Jemimah-b1y]

@MRDIAGNOSTECH Thanks, i've done all of these tests. the resistance on the signal wire is around 42ohms and sensor ground 18ohms, which I feel is a normal wire resistance. I began to suspect the DME, i changed the DME, but it was the same(fan not coming on). I tried to on the AC to observe if there would be a difference, NO! Just thinking, can a bad thermostat sensor be a cause?

[@MRDIAGNOSTECH]

@@Jemimah-b1y voltage drop using volts, not ohms. It should not exceed 0.100V.

[@Jemimah-b1y]

@MRDIAGNOSTECH woke up to see your response. Your responses are really insightful and helpful. Yeah, voltage drop btw sensor signal and Dme is 0.098v. with the ects unplugged, a measure btw the sensor signal wire and a good ground should give a 4.9v - 5.1v and a measure btw sensor ground and bat+ should give battery voltage(BMW manual) and that is what i'm getting. With the sensor plugged, i measure btw sensor signal(back probed), and ground gives 2.6v after an overnight sleep test. Pls where am i getting it wrong?

[@Rekani-sq5nl]

Thanks for explanation, well done

[@clementphiri1158]

What if you are getting 5v on the signal wire as well the ground wire at point B6. How do you fix that?

[@MAZMSPBRA]

Amazing! Another great video for beginners and advanced technicians! Keep up the great work! I may have to enroll to your classes for a refreshment soon!

[@Max-j2r]

❤❤❤❤❤❤

[@Outrunninaround.]

So usually heat creates resistance which lowers voltage. Here resistance drops and so does voltage.

[@MRDIAGNOSTECH]

@@Outrunninaround. That's because this is a negative coefficient temperature sensor.

[@ThunderbirdRocket]

Nice 👍🏼 ! 🔥 🧰
Thanks mate !

[@ericornelas5488]

GREAT VIDEO!!