Diagnosis And Testing - Ambient Temperature Sensor: Notes
The thermometer function is supported by the ambient temperature sensor, the Totally Integrated Power Module (TIPM), the Controller Area Network (CAN) data bus circuit, and the instrument cluster or Cab Compartment Node (CCN) compass/temperature display unit.
The system displays the last known temperature when starting the vehicle and may take some time/mileage to update to an accurate current reading, up to 5 minutes at a maintained speed above 40 mph (64.3 kph). Customers with very short commutes may not get an updated reading before the vehicle is turned off, or if the ignition does not remain in the OFF position for more than 255 minutes (4hrs. 15min.). This strategy was intended to eliminate wildly fluctuating readings and may cause some customer confusion leading to unnecessary diagnostics/parts replacements.
If the display shows " _ _ _ ", there is an OPEN or SHORT CIRCUIT that must be repaired. The ambient temperature sensor can be diagnosed using the following Sensor Test.