For 1990-2009 cars

### Circuit Description

Front Duct sensor allow the HVAC control module to monitor the temperature in the car.

### DTC Descriptors

This diagnostic procedure supports the following DTC :

DTC B0173 Duct Sensor Input Voltage

### Conditions for Running the DTC

Ignition is ON.

### Conditions for Setting the DTC

• | The HVAC control module determines that the value of the air temperature parameter is less than 0.27V or greater than 4.64V.

• | The HVAC control module detects a short to battery positive voltage in the Duct sensor.

• | The HVAC control module detects that the Duct sensor control circuit is open.

### Action Taken When the DTC Sets

The duct sensor value setting is 75 degrees.

### Conditions for Clearing the DTC

• | The DTC will become history if the HVAC control module no longer detects a fault.

• | Ignition is ON or OFF.

• | The DTC can be cleared with a scan tool.

### Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. Tests the voltage of the Duct sensor.

2. Tests the resistance of the Duct sensor.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
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 Duct sensor value in the Heating and Air Conditioning data list.

Does the scan tool indicate that the Duct sensor value is within the specified range?

0.27-4.64V

Go to Step 8

Go to Step 3

3 |

1. Turn OFF the ignition.
2. Disconnect the Duct sensor.
3. Turn ON the ignition, with the engine OFF.
4. With a scan tool, observe the Duct sensor data parameter.

Does the scan tool indicate that the Duct data parameter is greater than the specified value?

4.64V

Go to Step 4

Go to Step 5

4 |

1. Turn OFF the ignition.
2. Connect a fused jumper wire between the signal circuit of the Duct sensor and the low reference circuit of the Duct sensor.
3. Turn ON the ignition, with the engine OFF.
4. With a scan tool, observe the Duct sensor parameter.

Does the scan tool indicate that the Duct sensor value is less than the specified value?

0.27V

Go to Step 8

Go to Step 6

5 | Test the signal circuit of the Duct sensor for a short to ground. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9
6 | Test the signal circuit of the Duct sensor for a short to ground. Did you find and correct the condition? | 2.2V | Go to Step 12 | Go to Step 7
7 | Test the reference circuit of the Duct sensor for a high resistance or an open. Does the scan tool indicate the Duct sensor value is within the specified range? | 2.2Kohms | Go to Step 12 | Go to Step 9
8 | Inspect for poor connections at the harness connector of the Duct sensor. 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. Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 11
10 | Replace the Duct sensor. Did you complete the replacement? | -- | Go to Step 12 | --
11 | Replace the HVAC control module. Did you complete the replacement? | -- | Go to Step 12 | --
12 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK