GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

Schematic Reference: Headlights Schematics

Connector End View Reference: Lighting Systems Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Place the headlamp switch in the ON position.
  2. Place the dimmer switch in the high beam position.

Do the high beam headlamps operate normally?

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

Go to Step 3

3

Is only one high beam headlamp inoperative?

Go to Step 4

Go to Step 6

4

Test the high beam headlamp supply voltage circuit for high resistance, an open or a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 5

5

Test the high beam headlamp ground circuit for high resistance or an open . Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 10

6

  1. Disconnect the headlamp high relay.
  2. Connect a test lamp between the control circuit of the headlamp high relay and the battery positive voltage circuit of the headlamp high relay connector.

Does the test lamp illuminate?

Go to Step 15

Go to Step 7

7

Test for a poor connection or an open in the 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 17

Go to Step 8

8

  1. Connect the headlamp high relay.
  2. Test the headlamp dimmer switch signal and ground circuits for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct a condition?

Go to Step 17

Go to Step 9

9

  1. Place the headlamp switch in the ON position.
  2. Connect a fused jumper from ground to the headlamp dimmer switch signal terminal of the headlamp dimmer switch connector.

Do the high beam headlamps illuminate?

Go to Step 11

Go to Step 12

10

Inspect for poor connections at the harness connector of the inoperative blub. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 13

11

Inspect for poor connections at the harness connector of the headlamp dimmer switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 16

12

Inspect for poor connections at the harness connector of the body control module (BCM). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 17

Go to Step 14

13

Replace the high beam bulb. Refer to Headlamp Bulb Replacement or Sealed Beam Headlamp Replacement .

Did you complete the replacement?

Go to Step 17

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14

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 17

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15

Replace the headlamp high beam relay. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 17

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16

Replace the headlamp dimmer switch. Refer to Turn Signal Multifunction Switch Replacement in Steering Wheel and Column.

Did you complete the repair?

Go to Step 17

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17

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3