Ambient Temp Sensor: Operation

WARNING: This page is about a different car, the 2004 Dodge Grand Caravan, 2004 Dodge Caravan, and 2004 Chrysler Town & Country. 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 Front Control Module. The resistance in the sensor changes as temperature changes, changing the temperature sensor signal circuit voltage to the Front Control Module. Based upon the resistance in the sensor, the Front Control Module senses a specific voltage on the temperature sensor signal circuit, which it is programmed to correspond to a specific temperature. The Front Control Module then sends the proper ambient temperature messages to the EVIC, CMTC over the PCI J1850 data bus.

The thermometer function is supported by the ambient temperature sensor, a wiring circuit, the Front Control Module, the Programmable Communications Interface (PCI) data bus, and a portion of the Electronics module. If any portion of the ambient temperature sensor circuit fails, the Front Control Module will self-diagnose the circuit.

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 - OVERHEAD CONSOLE . For complete circuit diagrams, refer to the appropriate wiring information.