GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Install a scan tool.
  2. Cover the sunload sensor.
  3. Start the engine.
  4. Adjust driver side temperature to 24°C (75°F).
  5. Turn OFF the passenger HVAC control.
  6. With a scan tool, observe the Right and Left Solar Sensor data parameters in the instrument panel module Open/Short Data list.

Does the scan tool indicate that both the right and left solar sensor parameters are greater than the specified value?

230 Counts

Go to Step 3

Go to Step 13

3

  1. Uncover the sunload sensor.
  2. Direct a light source at the right and then the left side of the sunload sensor.

Do the counts change similarly and correspond to the proper side of the sunload sensor?

--

Go to Step 4

Go to Step 13

4

  1. Fully open all panel outlets.
  2. Select PANEL mode.
  3. Set blower speed to illuminate 2 bars on the fan speed display.
  4. Inspect for airflow through the inside air temp sensor by placing a 5 cm (2 in) square piece of paper over the sensor air inlet.

Does the paper stay in place?

--

Go to Step 5

Go to Step 12

5

  1. Turn OFF the ignition.
  2. Check right and left panel and heater temperature sensors for proper installation. Refer to Panel Discharge Sensor Replacement - Left Side , Panel Discharge Sensor Replacement - Right Side and Heater Temperature Sensor Replacement .

Did you find and correct the condition?

--

Go to Step 19

Go to Step 6

6

Inspect for poor connections/terminal tension at the right and left panel and heater temperature sensor harness connectors. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 7

7

Test the right and left panel and heater temperature sensor resistances. Refer to Sensor Resistance Table .

Do the resistances measure near the specified value?

--

Go to Step 8

Go to Step 17

8

Inspect for poor connections at the harness connector of the outside air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 9

9

Test the outside air temperature sensor resistance. Refer to Sensor Resistance Table .

Does the resistance measure near the specified value?

--

Go to Step 10

Go to Step 15

10

Inspect for poor connections at the harness connector of the inside air temp sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 11

11

Test the inside air temp sensor resistance. Refer to Sensor Resistance Table .

Does the resistance measure near the specified value?

--

Go to Step 18

Go to Step 16

12

Inspect for a blocked or disconnected aspiration hose.

Did you find and correct the condition?

--

Go to Step 19

--

13

Inspect for proper orientation (installation) and poor connections at the harness connector of the sunload sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 14

14

Replace the sunload sensor. Refer to Sunload and Twilight Sentinel Sensor Replacement in Instrument Panel, Gauges and Console.

Did you complete the replacement?

--

Go to Step 19

--

15

Replace the outside air temperature sensor. Refer to Ambient Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 19

--

16

Replace the inside air temp sensor. Refer to Inside Air Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 19

--

17

Replace the out of specification temperature sensor. Refer to Panel Discharge Sensor Replacement - Left Side , Panel Discharge Sensor Replacement - Right Side and Heater Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 19

--

18

  1. Start the engine.
  2. Operate the system. Refer to the appropriate procedure:

Does the system operate correctly?

--

System OK

Go to Symptoms

19

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2