GM Service Manual Online
For 1990-2009 cars only

Step

Action

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No

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

Connector End View Reference: Master Electrical Component List

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Turn ON the headlamps.
  2. Ensure that the headlamp dimmer switch is in the LOW position.

Do both low beam headlamps illuminate?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3

Is only one low beam headlamp inoperative?

Go to Step 13

Go to Step 4

4

  1. Disconnect the lamps switch assembly.
  2. Install a jumper between the headlamp switch headlamps ON signal circuit and ground.

Do the low beam headlamps illuminate?

Go to Step 9

Go to Step 5

5

Test for a poor connection , an open, or a short to battery positive voltage in the headlamp switch headlamps ON signal circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 6

6

  1. Reconnect the lamp switch assembly.
  2. Disconnect the body control module (BCM) connector C1.
  3. Install a jumper between the headlamp module control circuit and ground.

Do the low beam headlamps illuminate?

Go to Step 18

Go to Step 7

7

  1. Remove the headlamp module.
  2. Install a fused jumper between battery positive voltage and the switched low beam voltage supply circuit.

Do the low beam headlamps illuminate?

Go to Step 8

Go to Step 11

8

Test for the following in the headlamp module control circuit:

    • An open
    • A poor connection
    • A short to ground

Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 10

9

Inspect for a poor connection at the harness connector of the lamp switch assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 14

10

Inspect for a poor connection at the headlamp module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 15

11

Test for a short to ground in the low beam voltage supply circuit. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 12

12

Inspect for a poor connection at the harness connector of the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 19

Go to Step 17

13

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

Did you find and correct the condition?

Go to Step 19

Go to Step 16

14

Replace the lamp switch assembly. Refer to Headlamp Switch Replacement .

Did you complete the replacement?

Go to Step 19

--

15

Replace the headlamp module. Refer to Relay Replacement in Wiring Systems.

Did you complete the replacement?

Go to Step 19

--

16

Replace the inoperative low beam headlamp. Refer to Headlamp Assembly or Headlamp Bulb Replacement .

Did you complete the replacement?

Go to Step 19

--

17

Replace the underhood fuse block. Refer to Testing for Intermittent Conditions and Poor Connections .

Did you complete the replacement?

Go to Step 19

--

18

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

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