Circuit Description
The ambient air temperature sensor allows the HVAC control module to monitor the temperature of the air surrounding the front of the vehicle. The inside air temperature sensor assembly allows the HVAC control module to monitor the temperature of the air inside the passenger compartment. The inside air temperature assembly contains an electric fan which pulls the air from the passenger compartment to the sensor. 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 circuits. The HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. The HVAC control module also uses the ambient air temperature input to calculate the value of the ambient air temperature display. 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.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC B0159 Outside Air Temperature Sensor Circuit |
| • | DTC B0164 Passenger Compartment Temperature Sensor Circuit |
Conditions for Running the DTC
| • | Battery voltage to the HVAC control module is greater than 8.7 volts and less than 16.5 volts. |
| • | The ignition is turned ON. |
Conditions for Setting the DTC
The HVAC control module determines that the voltage applied to the input for the air temperature sensor is less than -40 to +215°C (-40 to +419°F).
Action Taken When the DTC Sets
| • | The driver information center (DIC) will display a default value of 75 in place of the ambient air temp sensor. |
| • | 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 the condition that set the DTC. |
| • | The history DTC will clear after 100 fault-free ignition cycles. |
| • | The DTC can be cleared with a scan tool. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Verifies that the temperature displayed is not within the calibrated range.
-
Tests for the proper operation of the circuit in the high voltage range.
-
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.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: HVAC Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
|
Important: For instant outside air temperature update simultaneously press Recirc, Rear Defog and fan up.
Does the scan tool indicate that the appropriate Air Temp. Sensor parameter is within the specified range? | -40 to +215°C (-40 to +19°F) | Go to Diagnostic Aids | Go to Step 3 | |
|
Important: For instant outside air temperature update simultaneously press Recirc, Rear Defog and fan up.
Does the scan tool indicate that the appropriate Air Temp. Sensor parameter is greater than the specified value? | 200°C (392°F) | Go to Step 4 | Go to Step 5 | |
|
Important: For instant outside air temperature update simultaneously press Recirc, Rear Defog and fan up.
Does the scan tool indicate that the appropriate Air Temp. Sensor parameter is less than the specified value? | -25°C (-13°F) | Go to Step 8 | Go to Step 6 | |
5 | Test the signal circuit of the appropriate air temperature sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
6 | Test the signal circuit of the appropriate air temperature sensor for a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 7 |
7 | Test the low reference circuit of the appropriate air temperature sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 |
8 | Inspect for poor connections at the harness connector of the appropriate air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 10 |
9 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11 |
10 | Replace the appropriate air temperature sensor. Refer to Ambient Air Temperature Sensor Replacement or Inside Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
