B3579

CIRCUIT DESCRIPTION
The rear HVAC control module monitors the air temperature in the upper auxiliary discharge duct via a 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 rear 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 controls 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 HVAC Control Module - Rear Auxiliary detects the signal circuit is less than 0.09 V (5 counts) or greater than 4.90 V (250 counts).

ACTION TAKEN WHEN THE DTC SETS
This test checks the Output temperature sensor value stored in the HVAC (ECC) controller. If the value stored is above the output max temperature value or below the minimum output temperature value, the DTC shall set. If the code is currently set, the actual sensor reading shall be displayed on the scan tool.

CONDITIONS FOR CLEARING THE DTC
- The DTC will become history if the HVAC Control Module - Rear Auxiliary 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.
- Refer to Testing for Intermittent and Poor Connections in Diagrams.

TEST DESCRIPTION

Steps 1-3:

Steps 4-12:

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