HVAC System - Automatic

DTC B0158

CIRCUIT DESCRIPTION
The ambient air temperature sensor provides the HVAC control module software with the temperature of the air outside the vehicle. That temperature can be displayed in the driver information center (DIC). A reference voltage is supplied to the sensor thermistor and the HVAC control module determines the voltage drop across that device which is proportional to temperature. As the air temperature increases, the resistance decreases and the voltage signal decreases. As the air temperature decreases, the resistance increases and the voltage signal increases. The inside air temperature sensor provides the HVAC control module with the temperature of the air drawn through an aspirator from the passenger compartment across a sensor. A reference voltage is supplied to the sensor thermistor and the HVAC control module determines the voltage drop across that device which is proportional to temperature. As the air temperature increases, the resistance decreases and the voltage signal decreases. As the air temperature decreases, the resistance increases and the voltage signal increases.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC B0158 Outside Air Temperature Sensor Circuit.
- DTC B0163 Passenger Compartment Temperature Sensor Circuit.




This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description. DTC Symptom Description

CONDITIONS FOR RUNNING THE DTC
The ignition is turned ON.

CONDITIONS FOR SETTING THE DTC

B0158
The HVAC control module detects the ambient air temperature sensor signal circuit is less than 2 counts for more than 30 seconds or more than 253 counts for more than 30 seconds.

B0163
The HVAC control module detects the inside air temperature sensor signal circuit is less than 2 counts or more than 253 counts for 30 seconds.

ACTION TAKEN WHEN THE DTC SETS
- The DIC will display 15°C (59°F) for outside air temperature.
- The DIC will display SERVICE A/C SYSTEM.

B0158
The system operates using a default value.

B0163
The system operates using a default value.

CONDITIONS FOR CLEARING THE DTC
- The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
- The history DTC will clear after 50 fault-free ignition cycles.
- The DTC can be cleared with a scan tool.

TEST DESCRIPTION

Step 1 - Step 9:

Step 10 - Step 13:

The numbers below refer to the step numbers on the diagnostic table.
3. This step tests for the proper operation of the circuit in the high voltage range.
4. This step 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.