GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

  1. Turn the headlamp switch to the ON position.
  2. Turn the headlamp dimmer switch to the LOW position.
  3. Using a test light, backprobe between the underhood accessory wiring junction block connector C3 terminal F12 to ground.

Does the test light illuminate?

--

Go to Step 2

Go to Step 3

2

Replace the underhood accessory wiring junction block. Refer to Underhood Electrical Center or Junction Block Replacement in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check - Lighting Systems

--

3

  1. Disconnect connector C201
  2. Using a test light, probe connector C201 terminal A3 (male side) to ground

Does the test light illuminate?

--

Go to Step 4

Go to Step 5

4

Using a test light, probe connector C201 terminal A2 to terminal A3 (male side).

Does the test light illuminate?

--

Go to Step 8

Go to Step 11

5

  1. Remove the headlamp switch, leaving the switch connected.
  2. Using a test light, backprobe the headlamp switch terminal D to ground.

Does the test light illuminate?

--

Go to Step 6

Go to Step 7

6

Repair a poor connection or an open in circuit 10 between the harness connector C201 terminal A3 and S221.

Is the repair complete?

--

Go to Diagnostic System Check - Lighting Systems

--

7

Using a test light, backprobe between the headlamp switch terminal A and ground.

Does the test light illuminate?

--

Go to Step 9

Go to Step 10

8

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

Is the repair complete?

--

Go to Diagnostic System Check - Lighting Systems

--

9

Replace the headlamp switch. Refer to Headlamp Switch Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - Lighting Systems

--

10

Repair a poor connection or an open in circuit 3240 between the headlamp switch connector terminal A and S235.

Is the repair complete?

--

Go to Diagnostic System Check - Lighting Systems

--

11

Repair a poor connection or an open in circuit 12 between the underhood accessory wiring junction block harness connector C2 terminal F12 and connector C201 terminal A2.

Is the repair complete?

--

Go to Diagnostic System Check - Lighting Systems

--