GM Service Manual Online
For 1990-2009 cars only

Step

Action

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Schematic Reference: Headlights/Daytime Running Lights (DRL) Schematics

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Turn the headlamp switch to the OFF position.

Do the low and high beam headlamps remain OFF?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Are the high beam headlamps ON at all times when the low beams are ON?

Go to Step 4

Go to Step 9

4

Disconnect the body control module (BCM) connector C1

Are the high beam headlamps illuminated?

Go to Step 5

Go to Step 6

5

Test for a short to ground in the headlamp high beam relay control circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 20

Go to Step 14

6

  1. Reconnect the BCM connector C1.
  2. Disconnect the turn signal/multifunction switch connector C2.

Are the high beam headlamp illuminated?

Go to Step 7

Go to Step 16

7

Test for a short to ground in the flash to pass switch signal circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 20

Go to Step 8

8

Test for a short to ground in the headlamp switch high beam signal circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 20

Go to Step 16

9

Disconnect the BCM connector C2.

Are the low beam headlamps ON?

Go to Step 10

Go to Step 11

10

Test for a short to ground in the headlamp low beam relay control circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 20

Go to Step 14

11

  1. Reconnect the BCM connector C2.
  2. Disconnect the turn signal/multifunction switch connector C3.

Are the low beam headlamps ON?

Go to Step 12

Go to Step 15

12

Test for the following in the headlamp switch OFF signal circuit:

    • An open
    • A poor connection
    • A short to battery positive voltage

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 20

Go to Step 13

13

Test for a short to ground in the headlamp switch headlamps ON signal circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 20

Go to Step 16

14

Inspect for poor connections at the underhood fuse block . Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 20

Go to Step 17

15

Inspect for poor connections at the turn signal/multifunction switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 20

Go to Step 18

16

Inspect for poor connections at the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 20

Go to Step 19

17

Replace the underhood fuse block. Refer to Underhood Electrical Center or Junction Block Bracket Replacement .

Did you complete the replacement?

Go to Step 20

--

18

Replace the turn signal/multifunction switch. Refer to Turn Signal Multifunction Switch Replacement .

Did you complete the replacement?

Go to Step 20

--

19

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the repair?

Go to Step 20

--

20

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3