GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

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

Connector End View Reference: Lighting Systems Connector End Viewsor Data Communication Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

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

Do the low beam headlamps operate normally?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Is only one low beam headlamp inoperative?

Go to Step 4

Go to Step 5

4

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

Did you find and correct the condition?

Go to Step 16

Go to Step 9

5

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

Does the test lamp illuminate?

Go to Step 14

Go to Step 6

6

  1. Connect the headlamp low relay.
  2. Disconnect the multifunction switch.
  3. Place the headlamp switch in the HEAD position.

Do the low beam headlamps illuminate?

Go to Step 10

Go to Step 7

7

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

Did you find and correct a condition?

Go to Step 16

Go to Step 8

8

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

Did you find and correct a condition?

Go to Step 16

Go to Step 11

9

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

Did you find and correct the condition?

Go to Step 16

Go to Step 12

10

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

Did you find and correct the condition?

Go to Step 16

Go to Step 15

11

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

Did you find and correct the condition?

Go to Step 16

Go to Step 13

12

Replace the inoperative bulb. Refer to Headlamp Assembly or Headlamp Bulb Replacement.

Did you complete the replacement?

Go to Step 16

--

13

Replace the BCM. Refer to Control Module References.

Did you complete the replacement?

Go to Step 16

--

14

Replace the low beam headlamp relay. Refer to Relay Replacement.

Did you complete the replacement?

Go to Step 16

--

15

Replace the headlamp dimmer switch. Refer to Turn Signal Multifunction Switch Replacement.

Did you complete the repair?

Go to Step 16

--

16

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3