Ambient Temperature Sensor / Switch HVAC: Description and Operation

Ambient Temperature Sensor:

Ambient air temperature is monitored by the Electronic Vehicle Information Center Computer (EVIC) through ambient temperature sensor messages received from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus network. The PCM receives a hard wired input from the ambient temperature sensor. The ambient temperature sensor is a variable resistor mounted in front the radiator, behind the grille, near the center of the vehicle.

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 five-volt reference sent to it by the Powertrain Control Module (PCM). The resistance in the sensor changes as temperature changes. This changes the temperature sensor return signal circuit voltage to the PCM. Based upon the resistance in the sensor, the PCM is programmed to correspond to a specific temperature. The PCM then sends the proper ambient temperature messages to the EVIC over the PCI data bus.

The thermometer function is supported by the ambient temperature sensor, a wiring circuit, the Powertrain Control Module (PCM), the Programmable Communications Interface (PCI) data bus, and a portion of the Electronic Vehicle Information Center (EVIC) Computer module.

The ambient temperature sensor circuit can also be diagnosed by referring to Diagnosis and Testing -Ambient Temperature Sensor, and Diagnosis and Testing - Ambient Temperature Sensor Circuit. 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 Computer.