Buick 2001 Park Avenue Owner's Manual page 301

To check the aim, the vehicle should be properly
prepared as follows:
D
The vehicle must have all four tires on a perfectly
level surface.
D
If necessary, pads may be used on an uneven surface.
D
The vehicle should not have any snow, ice or mud
attached to it.
D
The vehicle should be fully assembled and all other
work stopped while headlamp aiming is being done.
D
There should not be any cargo or loading of the
vehicle, except it should have a full tank of fuel and
one person or 160 lbs. (75 kg) on the driver's seat.
D
Close all doors.
D
Tires should be properly inflated.
D
Rock the vehicle to stabilize the suspension.
Start with the horizontal aim. The adjustment screws can be
turned with an E8 Torx R socket or T15 Torx screwdriver.
6-38
Once the horizontal aim is adjusted, then adjust the
vertical aim.
1. Turn the horizontal
aiming screw (A)
until the
indicator (B) is
lined up with zero.