B1318

CIRCUIT DESCRIPTION
The HVAC control processor monitors the outside light on the inside of the vehicle via a light sensitive photodiode which is called a sunload sensor. The HVAC control processor uses this information to compensate for the effect of the sun on the inside air temperature of the vehicle. When the sensor is in direct sunlight, the signal voltage is low. When the sensor is shaded, the signal voltage is high. The HVAC control processor requests A/C compressor clutch engagement and controls the air temperature actuator door positions in order to maintain the selected air temperature.

CONDITIONS FOR RUNNING THE DTC
The ignition is turned ON.

CONDITIONS FOR SETTING THE DTC
The HVAC control processor detects the signal circuit is 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 processor. The scan tool displays the default Solar Sensor value in the Heating and Air Conditioning Data list. The scan tool displays the actual Raw Solar Sensor value in the Heating and Air Conditioning, Open/Short Data list.

CONDITIONS FOR CLEARING THE DTC
^ The DTC will become history if the HVAC control processor no longer detects a failure.
^ The history DTC will clear after 100 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 Diagrams.

TEST DESCRIPTION

Steps 1-12:

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.