Ambient Temperature Sensor / Switch HVAC: Testing and Inspection

AMBIENT TEMPERATURE SENSOR
1. Turn the ignition switch to the OFF position. Disconnect and isolate the battery negative cable. Disconnect the ambient temperature sensor wire harness connector.
2. Measure the resistance of the ambient temperature sensor. At -40 °C (-40 °F), the sensor resistance is 336 kilo ohms. At 55 °C (140 °F), the sensor resistance is 2.488 kilo ohms. The sensor resistance should read between these two values. If OK, refer to Diagnosis and Testing - Ambient Temperature Sensor Circuit. If not OK, replace the faulty ambient temperature sensor.

AMBIENT TEMPERATURE SENSOR CIRCUIT
1. Turn the ignition switch to the OFF position. Disconnect and isolate the battery negative cable. Disconnect the ambient temperature sensor wire harness connector and the 22-way Body Control Module (BCM) wire harness connector.
2. Connect a jumper wire between the two terminals in the body half of the ambient temperature sensor wire harness connector.
3. Check for continuity between the sensor return circuit and the ambient temperature sensor signal circuit cavities of the 22-way BCM wire harness connector. There should be continuity. If OK, go to Step 4. If not OK, repair the open sensor return circuit or ambient temperature sensor signal circuit to the ambient temperature sensor as required.
4. Remove the jumper wire from the body half of the ambient temperature sensor wire harness connector. Check for continuity between the sensor return circuit cavity of the 22-way BCM wire harness connector and a good ground. There should be no continuity. If OK, go to Step 5. If not OK, repair the shorted sensor return circuit as required.
5. Check for continuity between the ambient temperature sensor signal circuit cavity of the 22-way BCM wire harness connector and a good ground. There should be no continuity. If OK, refer to Diagnosis and Testing - Electronic Vehicle Information Center. If not OK, repair the shorted ambient temperature sensor signal circuit as required.