B0179

DTC B0179

CIRCUIT DESCRIPTION
The following DTCs are for the air temperature sensors located in the discharge air ducts:
- B0174 is for the upper left air temperature sensor.
- B0179 is for the lower left air temperature sensor.
- B0510 is for the upper right air temperature sensor.
- B0515 is for the lower right air temperature sensor.

Air temperature sensors allow the HVAC control module to monitor the temperature of the discharge air in the HVAC ducts. The module applies 5 volts to internal input resistors that are connected to the signal circuits of the air temperature sensors. The module provides ground to the air temperature sensors through the low reference circuit. The HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. When the duct air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the duct air temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The HVAC control module converts the voltage values to count values where 1 V is approximately equal to 51 counts.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC B0174 Output Air Temperature Sensor (Upper Left) Circuit Range/Performance
- DTC B0179 Output Air Temperature Sensor 2 (Lower Left) Circuit Range/Performance
- DTC B0510 Output Air Temperature Sensor 3 (Upper Right) Circuit Range/Performance
- DTC B0515 Output Air Temperature Sensor 4 (Lower Right) Circuit Range/Performance

CONDITIONS FOR RUNNING THE DTC
- Battery voltage is within 8.7-16.5 V.
- The ignition is ON.

CONDITIONS FOR SETTING THE DTC
The HVAC control module determines that the value of the air temperature parameter is less than 5 counts or greater than 250 counts.

ACTION TAKEN WHEN THE DTC SETS
The HVAC control module uses a default air temperature value for further automatic control calculations. The default values are not displayed on the scan tool.

CONDITIONS FOR CLEARING THE DTC
- The DTC will become history if the HVAC control module no longer detects a fault.
- The history DTC will clear after 100 fault-free ignition cycles.
- The DTC can be cleared with a scan tool.

TEST DESCRIPTION

Steps 1-11:

Step 12:

The numbers below refer to the step numbers on the diagnostic table.
2. Verifies that the temperature displayed is not within the calibrated range.
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.