GM Service Manual Online
For 1990-2009 cars only

Low and High Beams Headlamps Inoperative Domestic

Step

Action

Yes

No

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

1

Did you perform the Lighting Systems Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Verify that the low and high beam headlamps are inoperative.

Do the headlamps operate normally?

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

Go to Step 3

3

  1. Move the headlamp switch to the HEAD position.
  2. Connect a test lamp to the headlamp supply voltage circuit terminal at any inoperative headlamp bulb connector. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

Go to Step 9

Go to Step 4

4

  1. Remove the headlamp power relay from the underhood fuse block.
  2. Connect a test lamp to the headlamp relay coil supply voltage circuit at the relay connector terminal. Refer to Electrical Center Identification Views and Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

Go to Step 7

Go to Step 5

5

  1. Disconnect the headlamp switch.
  2. Ensure that the switch is in the HEAD position.
  3. Test that the headlamp switch has continuity between the battery positive voltage circuit input terminal and the headlamp power relay coil supply voltage circuit output terminal and that these terminals are not internally shorted to the ground terminal. Refer to Circuit Testing in Wiring Systems.

Was a problem found?

Go to Step 6

Go to Step 15

6

Test the headlamp power relay for an internal short to the ground terminal. Refer to Circuit Testing in Wiring Systems.

Was a problem found?

Go to Step 16

Go to Step 11

7

Connect a test lamp between the relay connector terminals of the headlamp relay coil supply voltage circuit and ground circuit in the underhood fuse block. Refer to Electrical Center Identification Views and Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

Go to Step 8

Go to Step 12

8

Test the following circuits for an open, high resistance or short to ground. Refer to Circuit Testing in Wiring Systems.

    • Headlamp power relay battery positive voltage
    • Headlamp supply voltage

Was a problem found?

Go to Step 13

Go to Step 16

9

Test the headlamp dimmer switch signal circuit for continuity to ground. Refer to Circuit Testing in Wiring Systems.

Was a problem found?

Go to Step 10

Go to Step 17

10

Test the following circuits for an open or high resistance. Refer to Circuit Testing in Wiring Systems.

    • Headlamp dimmer switch signal
    • Headlamp dimmer switch ground

Was a problem found?

Go to Step 14

Go to Step 18

11

Repair the open, high resistance or short to ground in one of the following circuits. Refer to Wiring Repairs in Wiring Systems.

    • Headlamp switch battery positive voltage
    • Headlamp relay coil supply voltage

Did you complete the repair?

Go to Step 19

--

12

Repair the open or high resistance in the headlamp power relay ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

13

Repair the open, high resistance or short to ground in one of the following circuits. Refer to Wiring Repairs in Wiring Systems.

    • Headlamp power relay battery positive voltage
    • Headlamp supply voltage

Did you complete the repair?

Go to Step 19

--

14

Repair the open or high resistance in one of the following circuits. Refer to Wiring Repairs in Wiring Systems.

    • Headlamp dimmer switch signal
    • Headlamp dimmer switch ground

Did you complete the repair?

Go to Step 19

--

15

Replace the headlamp switch. Refer to Headlamp Switch Replacement .

Did you complete the repair?

Go to Step 19

--

16

Replace the headlamp power relay.

Did you complete the repair?

Go to Step 19

--

17

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

Did you complete the repair?

Go to Step 19

--

18

Replace the daytime running lamp (DRL) relay. Refer to Daytime Running Lamps (DRL) Relay Replacement .

Did you complete the repair?

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3

Low and High Beams Headlamps Inoperative Export

Step

Action

Yes

No

Schematic Reference: Headlights Schematics

1

Did you perform the Lighting Systems Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Verify that the low and high beam headlamps are inoperative.

Do the headlamps operate normally?

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

Go to Step 3

3

  1. Move the headlamp switch to the HEAD position.
  2. Connect a test lamp to the headlamp supply voltage circuit terminal at any inoperative headlamp bulb connector. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

Go to Step 9

Go to Step 4

4

  1. Remove the headlamp power relay from the underhood fuse block.
  2. Connect a test lamp to the headlamp relay coil supply voltage circuit at the relay connector terminal. Refer to Electrical Center Identification Views and Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

Go to Step 7

Go to Step 5

5

  1. Disconnect the headlamp switch.
  2. Ensure that the switch is in the HEAD position.
  3. Test that the headlamp switch has continuity between the battery positive voltage circuit input terminal and the headlamp power relay coil supply voltage circuit output terminal and that these terminals are not internally shorted to the ground terminal. Refer to Circuit Testing in Wiring Systems.

Was a problem found?

Go to Step 6

Go to Step 14

6

Test the headlamp power relay for an internal short to the ground terminal. Refer to Circuit Testing in Wiring Systems.

Was a problem found?

Go to Step 15

Go to Step 10

7

Connect a test lamp between the relay connector terminals of the headlamp relay coil supply voltage circuit and ground circuit in the underhood fuse block. Refer to Electrical Center Identification Views and Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

Go to Step 8

Go to Step 11

8

Test the following circuits for an open, high resistance or short to ground. Refer to Circuit Testing in Wiring Systems.

    • Headlamp power relay battery positive voltage
    • Headlamp supply voltage

Was a problem found?

Go to Step 12

Go to Step 15

9

Test the headlamp dimmer switch ground circuit for continuity to ground. Refer to Circuit Testing in Wiring Systems.

Was a problem found?

Go to Step 13

Go to Step 16

10

Repair the open, high resistance or short to ground in one of the following circuits. Refer to Wiring Repairs in Wiring Systems.

    • Headlamp switch battery positive voltage
    • Headlamp relay coil supply voltage

Did you complete the repair?

Go to Step 17

--

11

Repair the open or high resistance in the headlamp power relay ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

--

12

Repair the open, high resistance or short to ground in one of the following circuits. Refer to Wiring Repairs in Wiring Systems.

    • Headlamp power relay battery positive voltage
    • Headlamp supply voltage

Did you complete the repair?

Go to Step 17

--

13

Repair the open or high resistance in the headlamp dimmer switch ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 17

--

14

Replace the headlamp switch. Refer to Headlamp Switch Replacement .

Did you complete the repair?

Go to Step 17

--

15

Replace the headlamp power relay.

Did you complete the repair?

Go to Step 17

--

16

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

Did you complete the repair?

Go to Step 17

--

17

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3