GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

  1. Turn the headlamp switch to the HEAD position.
  2. Turn the headlamp dimmer switch to the LOW position.

Do the low beam headlamps operate properly?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

Determine if one low beam headlamp or both high beam headlamps are inoperative.

Is one low beam headlamp inoperative?

Go to Step 9

Go to Step 4

4

  1. Turn the headlamp switch to the HEAD position.
  2. Turn the headlamp dimmer switch to the LOW position.
  3. Use a test lamp in order to backprobe between C201 terminal E12 and ground.

Did the test lamp light?

Go to Step 5

Go to Step 6

5

Repair the following conditions in CKT 12 between C201 terminal E12 and the fuse block terminal C1:

    • An open
    • A poor connection

Has the repair been made and the system rechecked?

Go to Step 11

--

6

Inspect for the following conditions in CKT 12 between the headlamp dimmer switch and C201 terminal E12:

    • An open
    • A poor connection

Is there a poor connection or an open in CKT 12?

Go to Step 7

Go to Step 8

7

Repair the following conditions in CKT 12 between C201 terminal E12 and the headlamp dimmer switch:

    • A poor connection
    • An open

Has the repair been made and the system rechecked?

Go to Step 11

--

8

Replace the headlamp dimmer switch. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle in Steering Wheel and Column - Tilt.

Has the repair been made and the system rechecked?

Go to Step 11

--

9

Test for one of the following conditions in the power supply circuit of the inoperative headlamp:

    • An open
    • A Poor connection
    • A short to Ground

Did you find and correct the condition?

Go to Step 11

Go to Step 10

10

Replace the inoperative headlamp. Refer to Headlamp Replacement

Did you complete the repair?

Go to Step 11

--

11

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2