GMC 2010 Sierra - Manual (Page 520)

These standards apply only to vehicles sold in the
United States.
Federal law prohibits the following acts or the causing
thereof:
1. The removal or rendering inoperative by any
person, other than for purposes of maintenance,
repair or replacement, of any device or element of
design incorporated into any new vehicle for the
purpose of noise control, prior to its sale or delivery
to the ultimate purchaser or while it is in use; or
2. The use of the vehicle after such device or element
of design has been removed or rendered
inoperative by any person.
Among those acts presumed to constitute tampering are
the acts listed below.
Insulation:
. Removal of the noise shields or any underhood
insulation.
Engine:
. Removal or rendering engine speed governor,
if the vehicle has one, inoperative so as to allow
engine speed to exceed manufacturer
specifications.
Fan and Drive:
. Removal of fan clutch, if the vehicle has one,
or rendering clutch inoperative.
. Removal of the fan shroud, if the vehicle has one.
Air Intake:
. Removal of the air cleaner silencer.
. Modification of the air cleaner.
Exhaust:
. Removal of the muffler and/or resonator.
. Removal of the exhaust pipes and exhaust pipe
clamps.
Headlamp Aiming
The vehicle has a visual optical headlamp aiming
system. The aim of the headlamps have been preset at
the factory and should need no further adjustment.
However, if the vehicle is damaged in a crash, the aim
of the headlamps may be affected and adjustment may
be necessary.
If oncoming vehicles flash their high beams at you, this
may mean the vertical aim of your headlamps needs to
be adjusted.
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