Where is the temperature sensor
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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