GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

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

Connector End View Reference: Component Connector End Views

1

Inspect the headlamps.

Do the headlamps work?

--

Go to Step 3

Go to Step 2

2

Repair the headlamp system before completing this diagnostic table.

Did you complete the repair?

--

Go to Step 3

--

3

Inspect fuses Ef20 and Ef27.

Is either of the fuses open?

--

Go to Step 5

Go to Step 4

4

  1. Inspect for a short circuit and repair if necessary.
  2. Replace the open fuse.

Did you find and correct the condition?

--

System OK

--

5

  1. Turn the headlamps ON.
  2. Measure the voltage at fuses Ef20 and Ef27.

Does the voltage measure within the specified range?

11-14 V

Go to Step 7

Go to Step 6

6

Repair the open circuit between the headlamp switch and fuses Ef20 and Ef27.

Did you complete the repair?

--

System OK

--

7

  1. Disconnect the electrical connectors at the headlamp leveling motors.
  2. Turn the headlamps ON.
  3. Measure the voltage at terminal 5 of the headlamps.

Does the voltage available at both headlamp leveling motors measure within the specified range?

11-14 V

Go to Step 9

Go to Step 8

8

Repair the open circuit between fuses Ef20 and Ef27 and the headlamps.

Did you complete the repair?

--

System OK

--

9

With the headlamp leveling motors disconnected, measure the resistance between ground and terminal 6 of the headlamps.

Is the resistance equal to the specified value?

0 Ω

Go to Step 11

Go to Step 10

10

Repair the ground circuit for the headlamps.

Did you complete the repair?

--

System OK

--

11

  1. Turn the headlamps ON.
  2. With the headlamps, measure the voltage at terminal 3 of the headlamp connector.

Does the voltage measure within the specified range?

6.2-10.6 V

Go to Step 16

Go to Step 12

12

  1. Disconnect the headlamp leveling switch.
  2. Turn the headlamps ON.
  3. Measure the voltage at the connector 3 wire at the headlamp leveling switch connector.

Does the voltage measure within the specified range?

11-14 V

Go to Step 14

Go to Step 13

13

Repair the open circuit between the headlamp relay and the headlamp leveling switch.

Did you complete the repair?

--

System OK

--

14

  1. Turn the low-beam headlamps ON.
  2. With the headlamp leveling switch removed for testing and the electrical connector still connected, measure the voltage at the D-GN wire at the headlamp leveling switch with the switch dial set at 0.

Is the voltage within the specified range?

11-14 V

Go to Step 16

Go to Step 15

15

Replace the headlamp leveling switch.

Did you complete the replacement?

--

System OK

--

16

  1. Turn the low-beam headlamps ON.
  2. With the headlamp leveling switch removed for testing and the electrical connector still connected, measure the voltage at the D-GN wire at the headlamp leveling switch with the switch dial set at 3.

Is the voltage equal to the specified value?

4.5 V

Go to Step 17

Go to Step 15

17

Repair the open D-GN wire between the headlamp leveling switch and the headlamp leveling motors.

Did you complete the repair?

--

System OK

--