Circuit Description
The inside air temperature sensor is a thermistor that controls signal voltage to the HVAC programmer. The inside air temperature sensor contains an electric fan which pulls the air from the passenger compartment to the sensor. The HVAC programmer supplies voltage on circuit 734. When the sensor is cold, the resistance is high and the HVAC programmer will sense a high signal voltage at terminal F7 (Buick, Oldsmobile) or terminal D7 (Pontiac). When the sensor warms, resistance is reduced and the signal voltage is pulled low through circuit 1704. Signal voltage will vary from 5 V (open circuit) to 0 V (short circuit).
Conditions for Setting the DTC
| • | The ignition is ON. |
| • | DTC 010 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 MIL/DTC
| • | Using a Scan Tool . |
| • | A current DTC will clear when the diagnostic runs and does not fail. |
| • | HVAC programmer battery voltage is interrupted. |
Test Description
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Is the resistance within the range specified in the table? | -- | Go to Step 2 | Go to Step 5 |
2 |
Refer to Measuring Voltage in Wiring Systems. Does the voltage equal the specified value? | 5 V | Go to Step 3 | Go to Step 6 |
Did the DTC reset? | -- | Go to Step 4 | Go to Intermittents and Poor Connections | |
4 |
Is the HVAC replacement complete? | -- | System OK | -- |
5 | Replace the sensor. Refer to Ambient Temperature Sensor Replacement . Refer to Ambient Temperature Sensor Replacement . Is the repair complete? | -- | System OK | -- |
6 | Is the voltage greater than the specified value? | 5 V | Go to Step 7 | Go to Step 8 |
7 | Repair the short to the battery in CKT 734. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | System OK | -- |
8 | Measure the voltage between sensor terminal A and DLC terminal 4. Refer to Measuring Voltage in Wiring Systems. Does the voltage equal the specified value? | 5 V | Go to Step 9 | Go to Step 12 |
9 | Are all HVAC sensor DTCs present? | -- | Go to Step 10 | Go to Step 14 |
10 | Check CKT 1704 for an open. Refer to Testing for Continuity in Wiring Systems. Was an open found? | -- | Go to Step 14 | Go to Step 11 |
11 | Replace the HVAC programmer if CKT 1704 is OK. Refer to Programmer Replacement . Was the HVAC programmer replaced? | -- | System OK | -- |
12 | Measure the voltage between HVAC programmer terminal F7 (Buick, Oldsmobile or terminal D7 (Pontiac) and DLC terminal 4. Refer to Measuring Voltage in Wiring Systems. Does the voltage equal the specified value? | 5 V | Go to Step 13 | Go to Step 4 |
13 | Repair the open in CKT 734 (GRN/BLK). Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | System OK | -- |
14 | Repair the open in CKT 1704. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | System OK | -- |
