B3579

CIRCUIT DESCRIPTION
The auxiliary HVAC control module monitors the air temperature in the upper auxiliary discharge duct via an upper auxiliary air temperature sensor. When the air is cold, the sensor resistance and signal voltage are high. When the air is warm, the sensor resistance and signal voltage are low. The auxiliary HVAC control module converts this voltage to a digital signal that can be transmitted over the keyboard display driver (KDD) data bus to the HVAC control module. The HVAC control module contains the logic that monitors the auxiliary air temperature and is responsible for setting the DTC.

CONDITIONS FOR RUNNING THE DTC
The ignition is turned ON.

CONDITIONS FOR SETTING THE DTC
The auxiliary HVAC control module detects the signal circuit is less than 5 Counts (0.09 V) or greater than 250 Counts (4.90 V).

ACTION TAKEN WHEN THE DTC SETS
A default value will be used for the sensor data by the HVAC control module. The actual value of the sensor will be displayed on the Scan tool.

CONDITIONS FOR CLEARING THE DTC
- The DTC will become history if the auxiliary HVAC control module no longer detects a failure.
- The history DTC will clear after 50 fault free ignition cycles.
- The DTC can be cleared with a scan tool.

DIAGNOSTIC AIDS
Check the following conditions:
- Visually inspect the sensor for contamination or damage.
- Verify that air flow to sensor is not restricted.
- Verify that the sensor is installed properly.
- If condition not present refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.

TEST DESCRIPTION

Steps 1-3:

Steps 4-12:

The number(s) below refer to the step number(s) on the diagnostic table.
3. Tests for the proper operation of the circuit in the high voltage range.
4. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.