Ambient Air Temperature Sensor

The temperature function is supported by the ambient air temperature sensor, a wiring circuit, and the Body Control Module (BCM). If any portion of the ambient air 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 some time/mileage to update to an accurate current reading, up to 5 minutes at a maintained speed above 64 km/h (40 mph). 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 (4 hrs. 15 min.). This strategy was intended to eliminate wildly fluctuating readings and may cause some customer confusion leading to unnecessary diagnostics/parts replacements.

The ambient air temperature sensor circuit can be diagnosed using the following Sensor Test, and Sensor Circuit Test. If the temperature sensor and circuit are confirmed to be OK, but the temperature display is inoperative or incorrect, test the EVIC operation. Refer to CENTER, ELECTRONIC VEHICLE INFORMATION, DIAGNOSIS AND TESTING .

SENSOR TEST

Turn the ignition switch to the OFF position. Disconnect and isolate the negative battery cable. Disconnect the ambient air temperature sensor wire harness connector.

Measure the resistance of the ambient air 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 below. If not OK, replace the inoperative ambient air temperature sensor.

NOTE:

If the sensor is believed to be the issue, it needs to be unplugged from the connector and tested separately with an ohmmeter. The sensor resistance should read between 8.0 and 12.0 kilohms if testing at room temperature 21°C (70°F). Measure the sensor resistance at room temperature. The resistance should be between the minimum and maximum values at room temperature as shown in the following table. If the sensor resistance is outside of the range, then the sensor should be replaced.

Resistance Ranges for Ambient Temperature Sensor
Room Temp (°F)	Minimum Resistance (kΩ)	Maximum Resistance (kΩ)
50.0	17.2	22.8
54.5	14.9	20.7
59.0	13.6	18.0
63.5	11.8	16.4
68.0	10.8	14.3
72.5	9.5	13.1
77.0	8.6	11.4
81.5	7.6	10.5
86.0	7.0	9.2

SENSOR CIRCUIT TEST

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

Turn the ignition switch to the OFF position. Disconnect and isolate the negative battery cable. Disconnect the wire harness connectors from the ambient air temperature sensor and the BCM.
Connect a jumper wire between the two terminals in the body half of the ambient air temperature sensor harness connector.
Check for continuity between the sensor return circuit and the ambient air temperature sensor signal circuit cavities of the BCM harness connector. There should be continuity. If OK, go to Step 4 . If not OK, repair the open sensor return circuit or ambient air temperature sensor signal circuit to the ambient air temperature sensor as required.
Check for continuity between the ambient air 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. Refer to CENTER, ELECTRONIC VEHICLE INFORMATION, DIAGNOSIS AND TESTING . If not OK, repair the shorted ambient air temperature sensor signal circuit as required.