Temperature Sensor Input

A/C Pressure Sensor
An electronic A/C pressure switch is mounted on the discharge line (high side) of the A/C compressor hose assembly. Its output to the PCM is variable and is dependent upon pressure inside the line.

This sensor operates like other 3-wire sensors. The PCM applies a 5.0 volt reference and a ground for the sensor. Changes in the A/C refrigerant pressure will cause the A/C pressure sensor input to the PCM to vary. The PCM monitors the A/C refrigerant pressure signal circuit and can determine when the signal is outside of the range of the sensor. When the signal is out of range (high or low) for a period of time, the Body Control Module (SBM) will set DTC B1324.

The PCM communicates the status of the A/C system pressure to the body control module (SBM) via Class 2 serial data. A higher pressure results in a higher voltage output. The PCM monitors the A/C pressure to:

^ Disengage the A/C clutch if the pressures are high 2968 kPa (430 psi).
^ Disengage the A/C clutch if pressures are too low below 255 kPa (35 psi).

Inside Air Temperature Sensor
The inside air temperature sensor is a temperature-sensitive resistor like the ambient temperature sensor. As outside air temperature increases, resistance decreases. As outside air temperature decreases, resistance increases.

A hose connected to the inside air temperature sensor continually draws passenger compartment air over the sensor, increasing the accuracy of the temperature reading.

The heater and A/C programmer monitors the inside temperature signal and uses this information to help determine command signals.

Heater and A/C Temperature Sensors
The heater and A/C temperature sensors are used to monitor discharge temperatures from the heater and A/C outlets. These sensors are located in the left and right heater and A/C ducts. The heater and A/C programmer monitors the discharge temperature sensors, and uses this information to help determine command signals.

Ambient Air Temperature Sensor
The ambient air temperature sensor is a temperature-sensitive resistor whose resistance varies inversely with temperature. As outside air temperature increases, resistance decreases. As outside air temperature decreases, resistance increases.

The heater and A/C programmer monitors the outside temperature signal and uses this information to display outside temperature on the heater and A/C control VF display and helps determine command signals.

The ambient air temperature sensor value can be updated by pressing the OFF, AUTO and VENT buttons on the heater and A/C control assembly at the same time. This function will update ambient temperature sensor to the current temperature reading.

Sun Load Sensors
A sun load sensor is a light-sensitive photo-diode that monitors the heat load of the sun on the vehicle. The sensors are located on top of the instrument panel, on either side of the defroster grill where sunlight can reach the sensors

As sunlight intensity increases, the resistance of the sensor decreases. As sunlight intensity decreases, the resistance increases.

The heater and A/C programmer compares the sun load sensor reading to the inside temperature reading and then determines how much cooling is required to reach and maintain the desired SET temperature.