B0179

DTC B0159, B0164, B0174, B0179, B0510, or B0515

Circuit Description

Air temperature sensors allow the HVAC control module to monitor the discharge duct air, outside air and inside air temperatures. The HVAC control module provides ground to the air temperature sensor through the low reference circuit. The HVAC control module monitors the voltage drop across the air temperature sensor thermistor by supplying a 5 volt reference to the signal circuit of the air temperature sensor for automatic control calculations. When the air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the air temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The HVAC control module can read voltage values and count values where 1 volt is approximately equal to 51 counts.

* Outside Air Temperature Sensor refers to the ambient air temperature sensor.
* Passenger Compartment Temperature Sensor refers to the inside air temperature sensor.
* Output Air Temperature Sensor 1 refers to the upper left air temperature sensor.
* Output Air Temperature Sensor 2 refers to the lower left air temperature sensor.
* Output Air Temperature Sensor 3 refers to the upper right air temperature sensor.
* Output Air Temperature Sensor 4 refers to the lower right air temperature sensor.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

* DTC B0159 Outside Air Temperature Sensor Circuit Range/Performance
* DTC B0164 Passenger Compartment Temperature Sensor Circuit Range/Performance
* DTC B0174 Output Air Temperature Sensor 1 Circuit Range/Performance
* DTC B0179 Output Air Temperature Sensor 2 Circuit Range/Performance
* DTC B0510 Output Air Temperature Sensor 3 Circuit Range/Performance
* DTC B0515 Output Air Temperature Sensor 4 Circuit Range/Performance

Conditions for Running the DTC

* Battery voltage is within 8.7-16.5 volts.
* 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 air temperature sensors operate using a default value. 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

Step 1 - Step 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.