Cadillac 2002 DeVille Owner's Manual page 350

Headlamp Aiming
Your vehicle has a visual optical headlamp aiming system
equipped with horizontal aim indicators. The aim has been
preset at the factory and should need no further adjustment.
This is true even though your horizontal aim indicators may
not fall exactly on the "0" (zero) marks on their scales.
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If your vehicle is damaged in an accident, the headlamp
aim may be affected. Aim adjustment to the low beam
may be necessary if it is difficult to see lane markers
(for horizontal aim), or if oncoming drivers flash their
high beams at you (for vertical aim). If you believe your
-
headlamps need to be re aimed, we recommend that you
take your vehicle to your dealer for service. However, it
-
is possible for you to re aim your headlamps as
described in the following procedure.
NOTICE:
To make sure your headlamps are aimed
properly, read all the instructions before
beginning. Failure to follow these instructions
could cause damage to headlamp parts.