B0159

CIRCUIT DESCRIPTION
The instrument panel integration module (IPM) monitors the ambient air temperature through the ambient air temperature sensor. The ambient air temperature sensor is a variable resistor. The IPM supplies 5 volts to the ambient air temperature sensor signal circuit and provides a low reference circuit. 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 IPM displays the ambient air temperature on the HVAC control module.

CONDITIONS FOR RUNNING THE DTC
The ignition is turned ON.

CONDITIONS FOR SETTING THE DTC
The IPM detects the ambient air temperature sensor signal circuit is less than 0.09 volt (5 counts) or greater than 4.90 volts (250 counts).

ACTION TAKEN WHEN THE DTC SETS
^ A default value of 2.50 volts (128 counts) will be substituted for the ambient air temperature sensor data by the IPM. The Outside Air Temp. displayed on the scan tool is the default value. The Outside Air Temp displayed on the scan tool in the Open/Short Data list is the actual value.
^ The HVAC control module will display "- -"for ambient air temperature when OFF.
^ The HVAC control module will display the set temperature when ON.

CONDITIONS FOR CLEARING THE DTC
^ The DTC will become history if the IPM 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 the condition is not present, refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.

TEST DESCRIPTION

Steps 1-3:

Steps 4-12:

The numbers below refer to the step numbers on the diagnostic table.
2. The operating range of the sensor is between 0.09-4.90 volts. If the Scan tool displays a value between 0-0.08 volts or 4.91-5.0 volts, then the sensor is performing outside of its designed limits.
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.