GMC 2003 C4C042 Owner's Manual page 275

Among those acts presumed to constitute tampering are
the acts listed below.
Insulation:
D
Removal of the noise shields or any underhood
insulation.
Engine:
D
Removal or rendering engine speed governor
(if equipped) inoperative so as to allow engine
speed to exceed manufacturer specifications.
Fan and Drive:
D
Removal of fan clutch (if equipped) or rendering
clutch inoperative.
D
Removal of the fan shroud (if equipped).
Air Intake:
D
Removal of the air cleaner silencer.
D
Modification of the air cleaner.
Exhaust:
D
Removal of the muffler and/or resonator.
D
Removal of the exhaust pipes and exhaust
pipe clamps.
Engine Oil (Gasoline Engine)
You should check your engine oil level regularly; this is
an added reminder.
If the low oil light appears
on the instrument cluster, it
means you need to check
your engine oil level right
away. For more
information, see "Low Oil
Light" in the Index.
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