Grand Cherokee 2WD V8-4.7L VIN N (2000)
Ambient Temperature Sensor / Switch HVAC: Testing and Inspection
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.
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 kilohms. At 55°C (14°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 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. If not OK, repair the shorted ambient temperature sensor
signal circuit as required.
