GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 STS 🢒 Body Systems 🢒 Lighting 🢒 Headlamp Aiming

Object Number: 1489184 Size: SH

Aiming of each of the headlamps is done by turning the vertical (1) adjusting screw which moves the headlamp bulb in relation to the headlamp assembly. The adjusting screw is located inboard of the front fender wheelhouse panel. The high beam will be correctly aimed if the low beam is aimed properly.

Some state and local authorities have specific requirements for aiming the headlamps. These requirements must be followed.

Aiming Area Preparation

Choose an appropriate aiming area, then prepare the aiming screen:

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Object Number: 1489199 Size: SH
  • The aiming area should be darkened and large enough to accommodate the vehicle and an additional 7.62 m (25 ft) measured from the face of the headlamp capsules to the front of the screen.
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  • The floor on which the vehicle rests must be flat with the bottom of the screen.
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  • The aiming screen should be at least 1.52 m (5 ft) high by 3.66 m (12 ft) wide with a matte white surface well shaded from extraneous light, and properly adjusted to the floor on which the vehicle stands. The screen should be provided with a vertical centerline (3), 2 laterally adjustable vertical tapes (2), and one vertically adjustable horizontal tape (1).
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    Important: Adjust the horizontal line or tape (1) on the screen. for each vehicle tested. Vehicles of the same model and year may have different standing height for the headlamp.

  • The screen must be movable to be aligned parallel with the rear axle of the vehicle. This will allow for a horizontal line drawn perpendicular to the centerline of the screen to pass through the center point between the 2 headlamp capsules (4).
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  • After the aiming screen has been set up in a permanent location, paint or tape a reference line on the floor 7.62 m (25 ft) from the screen, to identify the proper location of the headlamp capsules (5) being aimed.

    • If a regular commercial aiming screen is not available, use a vertical wall having a clear uninterrupted area at least 1.83 m (6 ft) high by 3.66 m (12 ft) wide, finished with a washable non-gloss white paint.

    Vehicle Preparation

    Prepare the vehicle for adjusting the headlamp beam aim:


      Object Number: 1489189 Size: SH
    1. Verify that all the components are in place on the vehicle, if other service has been performed on the vehicle.
    2. The vehicle must have a full tank of gas.
    3. Verify that the tires are inflated to the proper pressures.
    4. Stop all other work on the vehicle.
    5. Position the vehicle squarely with the aiming screen and with the headlamp directly over the reference line which is painted or taped on the floor.
    6. Locate the vertical center line on the aiming screen (3) to be in line with the center of the vehicle (4). This can be accomplished by sighting through the center of the rear window and over the hood.

      7. Mark the vertical center of the front and rear windows with narrow tape. Use these marks as sights to locate the centerline of the vehicle. Move the vehicle or the screen until the center line of the screen comes into alignment with the 2 points.

    7. Close the doors.
    8. Rock the vehicle sideways to stabilize the suspension.
    9. Measure the height (6) from the floor to the aiming dots of the headlamps. Adjust the horizontal tape (1) on the aiming screen to match this dimension.
    10. Measure the distance (5) between the headlamp aiming dots. Position the vertical tapes (2) this distance equally to the right and left of the centerline.

    Headlamp Aiming Procedure
    1. Open the hood.
    2. Measure from the floor to the center of the headlamp bulb. Some headlamps have an aim dot marked on the headlamp lens.
    3. At the screen, measure from the floor and place the horizontal tape at the measured distance.
    4. Measure from the reference line on the floor to the left headlamp bulb centerline.
    5. At the screen, measure from the reference line and place the vertical tape at the measured distance.
    6. Measure from the reference line on the floor to the right headlamp bulb centerline.
    7. At the screen, measure from the reference line and place the vertical tape at the measured distance.

      8. Important: Do not cover the headlamp. This may cause excessive heat build up.


      Object Number: 476831 Size: SH
    8. Turn ON the low beam headlamps and block the light from projecting onto the screen from the passenger side headlamp.

      9. Object Number: 1489184 Size: SH

      Important: Horizontal headlamp adjustment does not exist.

    9. Adjust the vertical aim of the headlamps to the specifications required by the state and the local authorities, or as shown in step 8.
    10. Rotate the headlamp adjuster (1) to change the vertical aim of the headlamp.
    11. Repeat the aiming procedure for the passenger side headlamp while blocking the light from projecting onto the screen from the driver side headlamp.
    12. Close the hood.