GM Service Manual Online
For 1990-2009 cars only

Visual Aiming Procedure

    • All equipment for testing headlamps must comply with the SAE Recommended Practice for Headlamp Inspection Equipment.
    • If you use a headlamp testing machine, the machine should give results equivalent to the results obtained using the screen procedure.
    • The machine should be in good condition and be properly adjusted.
        Use the machine in accordance with the manufacturer's instructions.
    • Machines that use a photoelectric cell or cells to determine aim, should also include a visual screen on which you can project a beam pattern proportional to the beam appearance, and aim on a screen at 7.62 m (25 ft).
       - The screen should be plainly visible to the technician who is adjusting the headlamps.
       - The screen should have horizontal and vertical reference lines in order to permit visual evaluation of the headlamp beam.

Headlamp Aiming Location (Using Screen Method)

    • The aiming area should be darkened and large enough to allow for the vehicle and an additional 7.62 m (25 ft), measured from the face of the headlamps to the front of the screen.
    • The floor on which the vehicle rests must be parallel with the bottom of the screen.
        If the floor is not level, compensate accordingly.

Headlamp Aiming Screen

    • If you use a screen, the screen should be at least 1.52 m (5 ft) high x 3.66 m (12 ft) wide with a matte white finish, well shaded from extraneous light.
    • Properly adjust the screen to the floor on which the vehicle rests.
    • The screen should be moveable so that you can align the screen parallel to the rear axle of the vehicle.
    • Position the screen so that a horizontal line drawn perpendicular to the centerline of the screen will pass an equal distance midway between the two headlamps.
    • The screen should have the following items:
       - A vertical centerline
       - Two laterally adjustable vertical tapes
       - One vertically adjustable horizontal tape
    • If a regular commercial aiming screen is not available, the screen may consist of a wall having a clear, uninterrupted area at least 1.83 m (6 ft) x 3.66 m (12 ft) wide. The surface should be finished with a no-gloss white paint.
    • After the aiming screen has been set up and located, paint or tape a reference line on the floor 7.62 m (25 ft) from the screen. Park the vehicle with the front of the headlamps directly over this reference line.

Headlamp Aiming Procedure

  1. Park the vehicle square with the screen, with the headlamps directly over this reference line.
  2. Ensure that the components are in place if other work has been done on the vehicle.
  3. Ensure that the vehicle is on a level surface.
  4. Stop all other work on the vehicle.
  5. Ensure that the vehicle has half a tank, or less, of fuel.
  6. Close all of the doors.
  7. Rock the vehicle from side to side in order to stabilize the suspension and level the vehicle.
  8. Line up the centerline of the vehicle with the centerline of the aiming screen.
  9. • Mark the vertical center of the rear and front windows using tape.
    • Use these lines as sights in order to line up the centerline of the vehicle and the screen.
  10. Adjust the vertical tapes on the screen in order to match the vertical centerline of each low beam headlamp.
  11. Measure the distance from the centerline of the low beam lamp.

  12. Adjust the horizontal tapes on the screen in order to match the horizontal centerline of each low beam headlamp.
  13. Measure the height from the floor to the center of the low beam.

  14. Turn on the low beam headlamps.
  15. Observe the left and the top edges of the high intensity zone on the screen.
  16. Adjust the headlamps to the following specifications:
  17. • The top edge of the center of intensity on the screen for the low beam should be less than 101.6 mm (4 in) above or below the cross section of the headlamp centerlines.
    • The left edge of the center of intensity on the screen for the low beam should be less than 101.6 mm (4 in) to the left or right of the cross section of the headlamp centerlines.

    Object Number: 233587  Size: SH
  18. Use a Phillips screwdriver in order to aim the headlamps. The outboard adjusting gear (2) on the headlamp adjusts the headlamp vertically. The inboard adjusting gear (1) on the headlamp adjusts the headlamp horizontally.

Alternate Headlamp Aiming Procedure

Tools Required

J 25300-D Headlamp Aimer

Aim the headlamps properly in order to obtain the maximum road illumination and safety that is built into the headlamp system. The proper aiming of the headlamps is very important because even slight variations from recommended aiming may be hazardous to approaching motorists.

Observe the following conditions when inspecting or adjusting the headlamp aim.

    • Ensure that the vehicle is on a level surface.
    • Inflate the tires to the specified pressure. Refer to the tire placard located on the inside of the instrument panel compartment door.
    • If the vehicle will regularly carry a load or a trailer, ensure that the load or trailer is on the vehicle.
    • Clean the headlamps.
    • Follow state requirements for headlamp aiming.

Engineers designed the J 25300-D in order to accommodate all composite and sealed beam headlamps in any standard shape or size and in any configuration. Adapters provided in the kit accommodate different lamp shapes and sizes. Regardless of configuration, always aim the headlamps in pairs.

The J 25300-D kit includes mounting and adjustment instructions.

  1. Use the universal aimer on one of the following floors:
  2. • A level floor
    • A calibrated floor slope
  3. Select and assemble the universal adapter that matches the aiming pad pattern on the lens of the headlamp.

  4. Object Number: 233616  Size: MH
  5. Align the selected adapter to the aiming pads. Move the adjuster rod for each pad (1, 3) until the pad agrees with the adjustment rod setting number (2) located on the headlamp.
  6. On some lamps, the numbers are located along the lower edge or the vertical edge of the lens.


    Object Number: 233619  Size: MH
  7. In order to adjust the rods (2) to the required position, perform the following steps:
  8. 4.1. Turn the rods to the neutral position.
    4.2. Slide the rods in or out to the proper setting.
    4.3. In order to adjust the setting viewer (3) to an odd number, turn the adjustment rod clockwise (5).
    4.4. In order to adjust the setting view to an even number, turn the adjustment rod counterclockwise (6).

    Object Number: 233616  Size: MH
  9. Attach the J 25300-D . Use the correct adapter with the correct side aimer.
  10. Use the J 25300-D to place the aimers onto the respective sides. Ensure that all adjustment rods and the articulating suction cups (4) are contacting the aiming pads (1, 3). Remove the extension studs if necessary.

  11. Object Number: 233587  Size: SH
  12. Use a Phillips screwdriver to aim the headlamps according to the instructions included in the J 25300-D . The outboard adjusting gear (2) on the headlamp adjusts the headlamp vertically. The inboard adjusting gear (1) on the headlamp adjusts the headlamp horizontally.