Outside Temperature Display Sensor: Testing and Inspection

DIAGNOSIS AND TESTING - AMBIENT TEMPERATURE SENSOR

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.

NOTE: 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.

SENSOR TEST

1. Turn the ignition switch to the Off position. Disconnect and isolate the battery negative cable. Disconnect the ambient temperature sensor harness connector.
2. Measure the resistance of the ambient temperature sensor. At - 40° C (- 40° F), the sensor resistance is 336 kilohms. At 55° C (130° F), the sensor resistance is 2.488 kilohms. The sensor resistance should read between these two values. If OK, refer to SENSOR CIRCUIT TEST. If not OK, replace the inoperative ambient temperature sensor.

SENSOR CIRCUIT TEST

Refer to the appropriate wiring information for complete circuit schematic or connector pin-out information.

1. Transition the ignition switch to the OFF status. Disconnect and isolate the battery negative cable. Disconnect the wire harness connectors from the ambient temperature sensor and the BCM.
2. Connect a jumper wire between the two terminals in the body half of the ambient temperature sensor harness connector.
3. Check for continuity between the sensor return circuit and the ambient temperature sensor signal circuit cavities of the BCM harness connector. There should be continuity. If OK, go to 4. If not OK, repair the open sensor return circuit or ambient temperature sensor signal circuit to the ambient temperature sensor as required.
4. Check for continuity between the ambient temperature sensor signal circuit cavity of the BCM harness connector and a good ground. There should be no continuity. If OK, test the EVIC operation,Electronic Vehicle Information Center - Operation. If not OK, repair the shorted ambient temperature sensor signal circuit as required.