Grand Caravan V6-3.3L VIN R (2005)
Ambient Temperature Sensor / Switch HVAC: Description and Operation
Ambient Temp Sensor
Ambient air temperature is monitored by the overhead console through ambient temperature messages received from the Powertrain Control Module
(PCM) over the Programmable Communications Interface (PCI) data bus circuit. The PCM receives a hard wired input from the ambient temperature
sensor. The ambient temperature sensor is a variable resistor mounted to a bracket that is secured with a screw to the right side of the headlamp mounting
module grille opening, behind the radiator grille and in front of the engine compartment.
The ambient temperature sensor is a variable resistor that operates on a five-volt reference signal sent by the Powertrain Control Module (PCM). The
resistance in the sensor changes as temperature changes, changing the temperature sensor signal circuit voltage to the PCM. Based upon the resistance in
the sensor, the PCM senses a specific voltage on the temperature sensor signal circuit, which it is programmed to correspond to a specific temperature.
The PCM then sends the proper ambient temperature messages to the Electronic Vehicle Information Center (EVIC)/Compass Mini-Trip Computer
(CMTC) over the Programmable Communication Interface (PCI) data bus.
The thermometer function is supported by the ambient temperature sensor, a wiring circuit, the PCM, the PCI data bus, and the Electronics module. If
any portion of the ambient temperature sensor circuit fails, the PCM will self-diagnose the circuit.
The ambient temperature sensor circuit can also be diagnosed manually. If the temperature sensor and circuit are confirmed to be OK, but the
temperature display is inoperative or incorrect to determine the cause. For complete circuit diagrams, refer to the appropriate wiring information.
