GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Interior Lights Dimming Schematics

1

Did you perform the Lighting Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Verify the fault is present.

Does the system operate normally?

Go to Testing for Electrical Intermittents in Wiring Systems

Go to Step 3

3

Turn ON the park lamps .

Do the park lamps function properly?

Go to Step 4

Go to Park Lamps Inoperative

4

Remove and inspect the ILLUM fuse. Refer to Testing for Short to Ground in Wiring Systems.

Is the fuse open?

Go to Step 9

Go to Step 5

5

  1. Re-install the fuse.
  2. Ensure the panel dimmer rheostat is at maximum.
  3. Connect a test lamp from the ILLUM fuse to ground.

Does the test lamp illuminate?

Go to Step 7

Go to Step 6

6

Connect a test lamp (back probe) between the instrument panel dimmer switch output circuit at the headlamp and panel dimmer switch to a good ground.

Does the test lamp illuminate?

Go to Step 10

Go to Step 13

7

  1. Disconnect the instrument cluster.
  2. Connect a test lamp between the instrument panel dimmer switch output circuit and a good ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 11

8

Connect a test lamp between the instrument cluster ground circuit and a battery positive voltage circuit.

Does the test lamp illuminate?

Go to Step 14

Go to Step 12

9

  1. Repair the short to ground in the instrument panel lamp feed circuit. Refer to Wiring Repairs in Wiring Systems.
  2. Replace the fuse.

Did you complete the repair?

Go to Step 15

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10

Repair the open in the instrument panel lamps dimmer switch output circuit between the switch and the fuse. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 15

--

11

Repair the open in the instrument panel dimmer switch output circuit between the fuse and the cluster. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 15

--

12

Repair the open in the instrument cluster ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 15

--

13

Replace the headlamp and panel dimmer switch. Refer to Headlamp Switch Replacement .

Did you complete the repair?

Go to Step 15

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14

Replace the instrument cluster, lights as needed. Refer to Instrument Cluster Bulb Replacement in Instrument Panel, Gauges, and Console.

Did you complete the repair?

Go to Step 15

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15

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3