B0520

CIRCUIT DESCRIPTION
The HVAC control module (IPM) monitors the air temperature in the rear heater duct through the 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 HVAC control module requests A/C compressor clutch engagement through the PCM and controls the auxiliary air temperature actuator door position in order to maintain the temperature selected on the HVAC control module.

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 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 temperature displayed on the scan tool in the Instrument Panel Module HVAC Sensors data list will be the default value. The actual sensor reading will be displayed on the scan tool in the Instrument Panel Module Open/Short Data list.

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
If condition not present refer to Testing for Intermittent and Poor Connections in Diagrams.

TEST DESCRIPTION

Steps 1-4:

Steps 5-12:

The numbers below refer to the step numbers 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.