Ambient Temperature Sensor: Operation

WARNING: This page is about a different car, the 2004 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.

The ambient temperature sensor is a variable resistor that operates on a five-volt reference signal sent to it by the BCM. The resistance in the sensor changes as temperature changes, changing the temperature sensor signal circuit voltage to the BCM. Based upon the resistance in the sensor, the BCM senses a specific voltage on the temperature sensor signal circuit, which it is programmed to correspond to a specific temperature. The BCM then sends the proper ambient temperature messages to the EVIC over the PCI data bus.

The temperature 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 temperature reading of 130° F will appear in the EVIC display in place of the temperature when the sensor circuit is shorted. A temperature reading of -40° F will appear in the EVIC display in place of the temperature when the sensor circuit is open.

The ambient temperature sensor circuit can also be diagnosed by referring to DIAGNOSIS AND TESTING . If the temperature sensor and circuit are confirmed to be OK, but the temperature display is inoperative or incorrect, refer to DIAGNOSIS AND TESTING - ELECTRONIC VEHICLE INFORMATION CENTER . For complete circuit diagrams, refer to the appropriate wiring information.