Circuit Description

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The following DTCs are for the auxiliary air temperature sensors located in the auxiliary HVAC ducts:

B3579 is for the upper auxiliary air temperature sensor.
B3584 is for the lower auxiliary air temperature sensor.

The auxiliary air temperature sensors allow the auxiliary HVAC control module to monitor the temperature of the discharge air in the auxiliary HVAC ducts. The module applies 5 volts to internal input resistors that are connected to the signal circuits of the air temperature sensors. The module provides ground to the air temperature sensors through the low reference circuit. The auxiliary HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. When the duct air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the duct air temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The auxiliary HVAC control module converts the voltage values to count values where 1 V is approximately equal to 51 counts.