B3579

Steps 1-6:

Steps 7-12:

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 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
A default value of 2.50 V (127 counts) will be used for the sensor data by the HVAC control module. The sensor reading displayed on the scan tool in the HVAC data list will be this default value.

CONDITIONS FOR CLEARING THE DTC
- The DTC will become history if the 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.
- Refer to Testing for Intermittent and Poor Connections in diagrams.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
8. Tests for the possibility of a short to another 5 V reference circuit.