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How the coolant temperature sensor works by Howstuffinmycarworks.com

hi my name is Lauren with hot stuff and

my car works calm in today's video I

will explain how the coolant temperature

sensor works the coolant temperature

sensor is a thermistor the thermistor is

a resistor that varies the voltage

output as the temperature changes its

operation is very simple when the

temperature of your engine increases the

sensors resistance decreases when the

coolant temperature decreases its

resistance increases for example when

your coolant temperature in your engine

is at 32 degrees fahrenheit expect your

resistance to be between forty eight

hundred and sixty six hundred ohms when

your coolant temperature is around one

hundred and seventy-six degrees

Fahrenheit the sensor will range its

resistance from 270 to 380 ohms

higher temperatures will generally

decrease the resistance between the two

terminals when performing resistance

tests on the sensor it is important to

disconnect the electrical connector you

can test your coolant temperature sensor

by using the ohm setting on your

voltmeter this way you can test the

resistance between the two terminals if

you don't know where the sensor is

located it's most common location is

near the thermostat housing certain

vehicles will have the sensor on the

side of the cylinder head once you've

performed the initial resistance test

with the engine cold remove the

equipment instead of a side start the

vehicle and let it run for a few minutes

then turn it off and perform the

resistance test again now that the

engine is warmer the resistance between

the two terminals should be lower if the

resistance did not change that means you

have a bad sensor and it needs to be

replaced if the resistance test showed

that the sensor is responding to the

temperature changes then it's time to

move on and test the signal coming from

the ECM in this video I am referencing

to a two-wire sensor the ECM sends a

reference voltage to one of the two

wires at

to the sensor when the key is a neat

mission and then the on position this

wire should breed approximately five

volt if neither of the wires is at 5

volts in the on position the problem

could be as simple as a blown fuse or a

defective circuit inside the EC it is

also possible that there could be a bad

connection in between the signal wire

and the ECM you can trace this wire all

the way down to the ECM by referring to

your vehicle's wiring diagram the ECM

knows what your engine temperature is

through the signals sent by the sensor

for vehicles that are not equipped with

the temperature sending unit the ECM

uses a coolant temperature signal to

power the gauge on your dashboard thank

you for watching this video on the

coolant temperature sensor if you found

this on our YouTube channel please visit

our website how stuff in my car works

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