Mechanics

Coolant Temperature Sensor CTS

Easy to follow guide on how an automotive engine coolant sensor works, this information pertains to most vehicles.

A coolant temperature sensor is located near the upper coolant outlet of engine and sits in the flow of the hottest point in the cooling system, these locations will vary. Use Google Images to find the location for your particular car or use a repair manual.


Coolant Temperature Sensor

Two wires which are connected to the engine computer PCM deliver feedback data which is then used to adjust engine and emission management systems.


Coolant Temperature Sensor Two Wires

These wires are connected to the sensor using a plastic connector designed to absorb engine vibration without failing.


Coolant Temperature Sensor Connector

The sensor is easily removed for testing or replacement, please visit our coolant sensor replacement guide for further instructions.


Coolant Sensor

Helpful Information

The temperature sensor is comprised of a housing filled with a composite which varies the resistance through its internal circuit as temperatures increases or decreases, which also provides data to adjust the in-dash gauge to inform the driver on engine operating temperatures. In older models this operation was perform by a coolant sensor which had one wire that performed the gauge readings solely.

Also described as an ECTS (electronic coolant temperature sensor) these sensors are easily tested using a voltmeter that can read the ohms of resistance which can be compared to a new sensor or factory specifications.

When this sensor fails it will set a trouble code which is indicated by a service engine soon or check engine warning light and can cause engine run-ability problems, a coolant leak can cause a false reading as well due to the lack of liquid in the cooling system.

AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2015-05-05)