GM Service Manual Online
For 1990-2009 cars only

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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 11

4

Remove the high beam relay.

Do the high beam headlamps turn OFF?

Go to Step 5

Go to Step 10

5

  1. Reinstall the high beam relay.
  2. Disconnect the body control module (BCM) connector C1.

Are the high beam headlamps illuminate?

Go to Step 6

Go to Step 7

6

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 26

Go to Step 18

7

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

Are the high beam headlamp illuminated?

Go to Step 8

Go to Step 21

8

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 26

Go to Step 9

9

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 26

Go to Step 21

10

Test for a short to battery positive voltage in the high beam headlamp solenoid switched voltage supply circuit. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

Go to Step 26

Go to Step 19

11

Remove the low beam relay.

Do the low beam headlamps turn OFF?

Go to Step 12

Go to Step 17

12

  1. Reinstall the low beam relay.
  2. Disconnect the BCM connector C2.

Are the low beam headlamps ON?

Go to Step 13

Go to Step 14

13

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 26

Go to Step 18

14

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

Are the low beam headlamps ON?

Go to Step 15

Go to Step 20

15

Test for a short to battery positive voltage, poor connection, or an open in the headlamp switch OFF signal circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 26

Go to Step 16

16

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 26

Go to Step 21

17

Test for a short to battery positive in low beam headlamp ballast switched voltage supply circuit. Refer to Circuit Testing and to Wiring Repairs .

Did you find and correct the condition?

Go to Step 26

Go to Step 19

18

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

Did you find and correct the condition?

Go to Step 26

Go to Step 22

19

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

Did you find and correct the condition?

Go to Step 26

Go to Step 23

20

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 26

Go to Step 24

21

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 26

Go to Step 25

22

Replace the relay. Refer to Relay Replacement .

Did you complete the replacement?

Go to Step 26

--

23

Replace the underhood electrical center. Refer to Underhood Electrical Center or Junction Block Replacement .

Did you complete the replacement?

Go to Step 26

--

24

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

Did you complete the replacement?

Go to Step 26

--

25

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

Did you complete the repair?

Go to Step 26

--

26

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3