Diagnosis And Testing - Ambient Temperature Sensor: Notes
The temperature function is supported by the ambient temperature sensor, a wiring circuit and the Body Control Module (BCM) (also known as the Common Body Controller/CBC). If any portion of the ambient temperature sensor circuit fails or if the Controller Area Network (CAN) data bus information is missing, a (- -) will appear in the Electronic Vehicle Information Center (EVIC) display in place of the temperature. When the sensor is exposed to temperatures above 55° C (130° F), or if the sensor circuit is shorted, 55° C (130° F) will appear in the EVIC display in place of the temperature. When the sensor is exposed to temperatures below - 40° C (- 40° F) or if the sensor circuit is open, - 40° C (- 40° F) will appear in the EVIC display.
The system displays the last known temperature when starting the vehicle and may take a minimum time or 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 their destination is reached, or if the ignition does not remain in the OFF status 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 diagnosis and parts replacements.