Ambient Temperature Sensor Testing

The thermometer function is supported by the ambient temperature sensor, a wiring circuit, the Body Control Module (BCM), the Programmable Communications Interface (PCI) data bus, and a portion of the Electronic Vehicle Information Center (EVIC) module. If any portion of the ambient temperature sensor circuit fails, the BCM will self-diagnose the circuit. A "Short Circuit" message will appear in the EVIC display in place of the temperature when the sensor is exposed to temperatures above 55° C 131° F, or if the sensor circuit is shorted. An "Open Circuit" message 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.

The ambient temperature sensor circuit can also 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, refer to Electronic Vehicle Information Center Diagnosis.

Sensor Test
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 2.488k ohms. The sensor resistance should read between these two values. If OK, refer to Sensor Circuit Test. If not OK, replace the faulty ambient temperature sensor.

Sensor Circuit Test
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 Electronic Vehicle Information Center Diagnosis. If not OK, repair the shorted ambient temperature sensor signal circuit as required.