For 1990-2009 cars

### 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

The 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 | DTC Symptom Descriptor
--- | ---
03 | Voltage Below Threshold
06 | Short to Ground or Open
07 | Voltage Above Threshold

### 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 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.

### 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

The numbers below refer to the step numbers on the diagnostic table.

1. This step tests for the proper operation of the circuit in the high voltage range.

2. 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.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, observe the Appropriate Air Temp parameter in the Climate Control Panel, Open/Short Data list.

Does the scan tool indicate that the Appropriate Air Temp parameter is within the specified range?

2-253 Counts

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3 |

1. Turn OFF the ignition.
2. Disconnect the appropriate air temperature sensor.
3. Turn ON the ignition, with the engine OFF.
4. With a scan tool, observe the Appropriate Air Temp parameter.

Does the scan tool indicate that the Appropriate Air Temp parameter is greater than the specified value?

253 Counts

Go to Step 4

Go to Step 5

4 |

1. Turn OFF the ignition.
2. Connect a 3-amp fused jumper wire between the signal circuit of the appropriate air temperature sensor and the low reference circuit of the Appropriate Air Temperature sensor.
3. Turn ON the ignition, with the engine OFF.
4. With a scan tool, observe the Appropriate Air Temp parameter.

Does the scan tool indicate that the Appropriate Air Temp parameter is less than the specified value?

2 Counts

Go to Step 9

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 13 | Go to Step 10
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 13 | 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 13 | Go to Step 8
8 | Test the following signal circuits for a short to voltage:

• | Evaporator temperature sensor

• | Ambient air temperature sensor

• | Inside air temperature sensor

• | Left sunload sensor

• | Right sunload sensor

• | Ambient light sensor

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 13

Go to Step 10

9 | 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 13 | Go to Step 11
10 | 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 13 | Go to Step 12
11 | Replace the appropriate air temperature sensor. Refer to Inside Air Temperature Sensor Replacement or Ambient Air Temperature Sensor Replacement . Did you complete the replacement? | -- | Go to Step 13 | --
12 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 13 | --
13 |

1. Clear the DTCs with the scan tool.
2. Operate the vehicle under conditions when DTC runs as specified in supporting documents.

Does the DTC set again?

--

Go to Step 2

System OK