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 in Wiring Systems

1

Did you perform the Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

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 in Wiring Systems

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 12

4

Is only one high beam headlamp ON?

Go to Step 19

Go to Step 5

5

Remove the high beam relay.

Do the high beam headlamps turn off?

Go to Step 6

Go to Step 11

6

  1. Reinstall the high beam relay.
  2. Disconnect the BCM connector C1.

Are the high beam headlamps illuminate?

Go to Step 7

Go to Step 8

7

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

Did you find and correct the condition?

Go to Step 24

Go to Step 20

8

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

Are the high beam headlamp illuminated?

Go to Step 9

Go to Step 23

9

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

Did you find and correct the condition?

Go to Step 24

Go to Step 10

10

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

Did you find and correct the condition?

Go to Step 24

Go to Step 23

11

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 21

12

Remove the low beam relay.

Do the low beam headlamps turn OFF?

Go to Step 13

Go to Step 18

13

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

Are the low beam headlamps ON?

Go to Step 14

Go to Step 15

14

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

Did you find and correct the condition?

Go to Step 24

Go to Step 20

15

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

Are the low beam headlamps ON?

Go to Step 16

Go to Step 22

16

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 in Wiring Systems.

Did you find and correct the condition?

Go to Step 24

Go to Step 17

17

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

Did you find and correct the condition?

Go to Step 24

Go to Step 23

18

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

Did you find and correct the condition?

Go to Step 24

Go to Step 21

19

Replace the headlamp. Refer to Headlamp Assembly or Headlamp Bulb and/or Cornering, Sidemarker, Park, Turn Signal Bulb Replacement .

Did you complete the repair?

Go to Step 24

--

20

Replace the relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 24

--

21

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

Did you complete the replacement?

Go to Step 24

--

22

Replace the turn signal/multifunction switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 24

--

23

Important: After replacing the BCM, perform the setup procedure. Refer to Body Control Module (BCM) Programming/RPO Configuration in Computer/Integrating Systems.

Replace the BCM. Refer to Body Control Module Replacement in Computer/Integrating Systems.

Did you complete the repair?

Go to Step 24

--

24

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3