GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

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

1

Did you perform the Lighting System Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

  1. Turn the ignition to the OFF position.
  2. Turn the headlamp switch to the HEAD position.
  3. Place the headlamp dimmer switch in the low beam position.

Are the low beam headlamps operating properly?

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

Go to Step 3

3

Is only one low beam headlamp inoperative?

Go to Step 6

Go to Step 4

4

Using a test lamp connected to a battery voltage, backprobe the headlamp low beam signal circuit that feeds the fuse block - underhood connector C2.

Does the test lamp illuminate?

Go to Step 10

Go to Step 5

5

Test for a high resistance or an open in the low beam signal circuit 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 16

Go to Step 11

6

  1. Disconnect the inoperative head lamp.
  2. Using a test lamp connected to a known good ground, probe the battery positive voltage circuit of the inoperative low beam headlamp .

Does the test lamp illuminate?

Go to Step 7

Go to Step 12

7

Using a test lamp, probe between the headlamp low beam signal circuit and the battery positive voltage circuit of the inoperative low beam headlamp .

Does the test lamp illuminate?

Go to Step 9

Go to Step 8

8

Test for a high resistance or an open in the headlamp low beam signal circuit of the inoperative low beam headlamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 10

9

Inspect for poor connections at the harness connector of the inoperative headlamp. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 13

10

Inspect for poor connections at the harness connector of the fuse block - underhood. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 14

11

Inspect for poor connections at the harness connector of the headlamp dimmer switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 16

Go to Step 15

12

Repair a high resistance or an open in the battery positive voltage circuit of the inoperative headlamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Has the repair been made?

Go to Step 16

--

13

Replace the inoperative 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 16

--

14

Replace the fuse block - underhood. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems.

Did you complete the repair?

Go to Step 16

--

15

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

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 2