GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

1

Check the high beam headlamps in the "flash-to-pass" mode.

Do the high beam headlamps work in the "flash-to-pass" mode?

--

Go to Step 2

Go to Step 3

2

Replace the headlamp combination switch.

Is the repair complete?

--

System OK

--

3

Check fuse Ef4.

Is fuse Ef4 blown?

--

Go to Step 4

Go to Step 5

4

  1. Check for a short circuit. Repair it, if necessary.
  2. Replace the fuse.

Is the repair complete?

--

System OK

--

5

Temporarily substitute the illumination lamp relay in place of the headlamp high relay.

Do the headlamps operate with the substituted relay?

--

Go to Step 6

Go to Step 7

6

Reinstall the illumination lamp relay in its original position, and install a new headlamp relay.

Is the repair complete?

--

System OK

--

7

  1. Install the headlamp high relay.
  2. Check the voltage at headlamp switch connector terminal 4.

Does the voltage equal the value specified?

11-14 V

Go to Step 9

Go to Step 8

8

Repair the open circuit between headlamp high relay terminal 86 and headlamp switch connector terminal 4.

Is the repair complete?

--

System OK

--

9

  1. Disconnect the headlamp connector.
  2. Turn the headlamp switch to the high-beam position.
  3. Use an ohmmeter to check the continuity between terminals 6 and 4 of the headlamp switch.

Does the ohmmeter indicate the value specified?

0 ohms

Go to Step 10

Go to Step 2

10

  1. Connect the headlamp switch connector.
  2. Turn the headlamp switch to the high-beam position.
  3. Check the voltage at the light switch connector terminal 2.

Does the voltage equal the value specified?

11-14 V

Go to Step 12

Go to Step 11

11

Repair the open circuit between the headlamp switch connector terminal 6 and light switch connector terminal 2.

Is the repair complete?

--

System OK

--

12

  1. Disconnect the light switch connector.
  2. Turn the headlamp switch to the high-beam position.
  3. Use an ohmmeter to check the continuity between terminals 2 and 3 of the light switch.

Does the ohmmeter indicate the value specified?

0 ohms

Go to Step 13

Go to Step 2

13

Repair the open circuit between fuse Ef24 and the high beam headlamps.

Is the repair complete?

--

System OK

--

14

  1. Turn the high beam headlamps on.
  2. Check the voltage at headlamp terminal 1 with the high beams selected.

Does the voltage available at the headlamp connector terminal 1 equal the value specified?

11-14 V

Go to Step 16

Go to Step 15

15

Repair the open circuit between fuse Ef24 and the high beam headlamps.

Is the repair complete?

--

System OK

--

16

  1. Disconnect the headlamp connectors.
  2. Connect an ohmmeter between the ground and the headlamp connector terminal 3.

Is the resistance equal to the value specified?

0 ohms

Go to Step 18

Go to Step 17

17

Repair the open circuit between the ground and the headlamp connector terminal 3.

Is the repair complete?

--

System OK

--

18

Replace the faulty headlamps.

Is the repair complete?

--

System OK

--