GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

1

Check fuses Ef17 (left-side headlamps) and Ef18 (right-side headlamps).

Is fuse Ef17 or Ef18 blown?

--

Go to Step 2

Go to Step 3

2

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

Is the repair complete?

--

System OK

--

3

Check the voltage at fuses Ef17 and Ef18.

Does the voltage available at fuses Ef17 and Ef18 equal the value specified?

11-14 V

Go to Step 14

Go to Step 4

4

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

Do the headlamps operate with the substituted relay?

--

Go to Step 5

Go to Step 6

5

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

Is the repair complete?

--

System OK

--

6

  1. Install the headlamp low relay.
  2. Check the voltage at headlamp switch connector terminal 5.

Does the voltage equal the value specified?

11-14 V

Go to Step 8

Go to Step 7

7

Repair the open circuit between low headlamp relay terminal 86 and headlamp switch connector terminal 5.

Is the repair complete?

--

System OK

--

8

  1. Disconnect the headlamp switch connector.
  2. Select the low beams.
  3. Use an ohmmeter to check the continuity between terminals 6 and 5 of the headlamp switch.

Does the ohmmeter indicate the value specified?

0 ohms

Go to Step 10

Go to Step 9

9

Replace the headlamp switch.

Is the repair complete?

--

System OK

--

10

  1. Connect the headlamp switch connector.
  2. 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 light switch to the low-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 9

13

Repair the open circuit between ground and light switch connector terminal 3.

Is the repair complete?

--

System OK

--

14

  1. Disconnect both headlamp connectors.
  2. Turn the headlamps on.
  3. Select the low beams.

Does the voltage at each headlamp connector terminal 2 equal the value specified?

11-14 V

Go to Step 16

Go to Step 15

15

Repair the open circuit between fuses Ef17 or Ef18 and the low 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

--