For 1990-2009 cars
HVAC Components
HVAC Air Delivery/Temperature Control Schematics Buick
HVAC Air Delivery/Temperature Control Schematics Buick, Oldsmobile
Handling ESD Sensitive Parts Notice
Data Link Connector Schematics
HVAC Air Delivery/Temperature Control Schematics Buick
HVAC Air Delivery/Temperature Control Schematics Buick, Oldsmobile

### Circuit Description

The inside air temperature sensor is a thermistor that controls signal voltage to the HVAC programmer. The inside air temperature sensor system contains an aspirator which pulls the air from the passenger compartment through the sensor. The HVAC programmer supplies voltage on CKT 734. When the sensor is cold, the resistance is high and the HVAC programmer will sense a high signal voltage at terminal B4. When the sensor warms, resistance is reduced and the signal voltage is pulled low through CKT 61. Signal voltage will vary from 5 V (open circuit) to 0 V (short circuit).

### Conditions for Setting the DTC

• | The ignition is ON.

• | DTC B1010 is not set.

• | Circuit short or open.

### Action Taken When the DTC Sets

• | A default value of 24°C (75°F) will be used by the HVAC programmer.

• | The default value allows the system to operate.

### Conditions for Clearing the DTC

• | Using a Scan Tool .

• | A history DTC will clear when 50 consecutive ignition cycles have occurred without a malfunction.

• | HVAC programmer battery voltage is interrupted.

### Test Description

1. This step ensures that the DTC was not set in error.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 |

1. Turn the ignition switch to the OFF position.
2. Disconnect the inside air temperature sensor.
3. Use a J 39200 digital multimeter (DMM) in order to measure the resistance between the sensor terminal A and terminal B. Refer to Troubleshooting with a Digital Multimeter .

Refer to Sensor Resistance Table . Is the resistance within the specified range according to the table?

--

Go to Step 3

Go to Step 2

2 | Replace the sensor. Refer to Inside Air Temperature Sensor Replacement . Is the repair complete? | -- | System OK | --
3 |

1. Turn the ignition switch to the ON position.
2. Use a J 39200 digital multimeter (DMM) in order to measure the voltage between terminal A and terminal B of the sensor harness connector. Refer to Measuring Voltage in Wiring Systems.

Is the voltage approximately equal to the specified value?

5 V

Go to Step 4

Go to Step 8

4 |

1. Turn the ignition switch to the OFF position.
2. Reconnect the inside air temperature sensor.
3. Turn the ignition switch to the ON position.
4. Clear the DTC using a Scan Tool .
5. Turn the ignition switch to the OFF position.
6. Turn the ignition switch to the ON position.

Does the DTC reset?

--

Go to Step 5

Go to Intermittents and Poor Connections Diagnosis

5 | Inspect all of the related connectors for proper terminal contact. Refer to Intermittents and Poor Connections . Is the terminal contact correct? | -- | Go to Step 6 | Go to Step 7
6 | Replace the HVAC programmer. Refer to Programmer Replacement . Is the repair complete? | -- | System OK | --
7 | Correct the terminal contact. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems. Is the repair complete? | -- | System OK | --
8 | Is the voltage greater than the specified value? | 5 V | Go to Step 9 | Go to Step 10
9 | Repair the short to battery in CKT 734. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | System OK | --
10 | Use a J 39200 digital multimeter (DMM) in order to measure the voltage between sensor terminal A and the DLC terminal 4. Refer to Measuring Voltage in Wiring Systems. Is the voltage approximately equal to the specified value? | 5 V | Go to Step 14 | Go to Step 11
11 | Use a J 39200 digital multimeter (DMM) in order to backprobe and measure the voltage between the HVAC programmer terminal B4 and the DLC terminal 4. Refer to Probing Electrical Connectors and Measuring Voltage in Wiring Systems. Is the voltage approximately equal to the specified value? | 5 V | Go to Step 12 | Go to Step 13
12 | Repair the open in CKT 734. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | System OK | --
13 | Replace the HVAC programmer. Refer to Programmer Replacement . Did you replace the programmer? | -- | System OK | --
14 | Are all of the sensor DTCs present? | -- | Go to Step 15 | Go to Step 17
15 | Inspect CKT 61 for opens. Is the circuit OK? | -- | Go to Step 16 | Go to Step 17
16 | Replace the HVAC programmer. Refer to Programmer Replacement . Is the repair complete? | -- | System OK | --
17 | Repair the open in CKT 61. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | System OK | --