GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check

2

When performing the Diagnostic System Check, was DTC B2646 displayed for the Instrument Panel Module?

Go to Diagnostic Trouble Code (DTC) List/Type in Lighting Systems

Go to Step 3

3

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, perform the WOW Instrument Cluster command in Instrument Panel Cluster special functions.

Do all HVAC control head segments illuminate?

Go to Step 4

Go to Step 7

4

When performing the WOW Instrument Cluster command, do all other VF displays illuminate?

Go to Step 5

Go to Symptoms in Lighting Systems

5

  1. Cover the sun load sensor.
  2. Turn ON the lights.

Is there backlighting?

Go to Step 6

Go to Symptoms in Lighting Systems

6

Adjust the dimming control from minimum to maximum intensity.

Does the VF display increase and decrease in intensity?

System OK

Go to Step 7

7

Inspect for poor connections at the harness connector of the heater and A/C control. 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 9

Go to Step 8

8

Replace the heater and A/C control. Refer to Control Assembly Replacement .

Did you complete the repair?

Go to Step 9

--

9

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2