Outside Ambient Temperature Sensor Explained

**LWM** · 08-09-2011, 04:15 PM

First the location of the sensor - just behind the right most section of the grill - see pictures attached. To remove it you can reach under the front fender and grab the assembly - twist and pull it slightly to the rear and it will come loose. It will now hang down below the fender. Remove the sensor from the wires by holding down the small tab and pull the sensor away from the wires. When reinstalling be sure to use the right side tab not the one behind the second grill opening - don't ask how I know

The sensor is a Thermistor - opposite of a resistor - the hotter it gets the less resistance it has.

DIAGNOSIS AND TESTING - AMBIENT TEMPERATURE SENSOR
Part Number 56042395
Turn the ignition switch to the Off position.
Disconnect the ambient temperature sensor wire harness connector.
Measure the resistance of the ambient temperature sensor. At –40° C (–40° F), the sensor resistance is 336.6 K ohms. At 60° C (140° F), the sensor resistance is 2.49 K ohms. The sensor resistance should read between these two values. If not OK, replace the faulty ambient temperature sensor. (at about 78 degrees F mine read 8.5K ohms)
If the resistance seems OK, make sure the connector contacts on sensor and loom are clean and have no corrosion. With the sensor unplugged turn on the ignition, the temp should read OC. Short the connector where the sensor would be and check the temp it should read SC

How the CNN (computer circuit/ display) works
Vehicle with the key off for more than 4 hours...The CCN will
update the ambient temperature reading immediately.

Vehicle with key off for more than 2 hours but less than 4
hours....The CCN will update the ambient temperature reading
immediately after vehicle reaches above 20 mph (with no duration
constraint) and will update every 500 ms (1/2 second) thereafter.

Vehicle with the key off for less than 2 hours...The CCN will
display the last temperature reading (which is stored in memory)
just prior to the ignition being turned off. The CCN will not
update the value in the display until the car has been driven at
20 MPH or above for 3 consecutive minutes. If the vehicles
speed and drive time does not meet the criteria the CCN will
continue to display the stored value until the criteria is met.
Once the criteria is met, then the CCN will update the display
every 500 ms based off of the ambient temperature sensor output.

(This confuses most of us when driving on short trips)
They probably want some air flowing past the sensor after sitting in front of a hot engine to get the correct temperature before showing the temperature on the display.