Ambient Temperature Sensor
Ambient air temperature is monitored by the CMTC through ambient temperature sensor messages received from the BCM over the PCI data bus network. The ambient temperature sensor is a variable resistor mounted in front of the radiator, behind the grille, near the center of the vehicle. See BODY CONTROL MODULES - LIBERTY article. The ambient temperature sensor cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.
The ambient temperature sensor is a variable resistor that operates on a 5-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 CMTC over the PCI data bus. The thermometer function is supported by the ambient temperature sensor, a wiring circuit, the BCM, the PCI data bus, and a portion of the CMTC. See Fig 1 .