GMC C series 2002 Owner's Manual page 117

Change Oil Light (If Equipped)
If the CHANGE OIL light comes on and stays on after
you start the engine, have the oil changed.
For additional information, see "Engine Oil, When to
Change" in the Index. To reset the Oil Life Monitor, see
"Engine Oil Life Monitor" in the Index.
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The CHANGE OIL light
should come on briefly
as a bulb check when you
start the engine. If the
light doesn't come on,
have it serviced.
Reduced Engine Power Warning Light
If the REDUCED ENGINE POWER light is on, but
there is no reduction in performance, proceed to your
destination. The performance may be reduced the next
time the vehicle is driven. The vehicle may be driven at
a reduced speed while the REDUCED ENGINE
POWER light is on, but acceleration and speed may
be reduced.
Anytime the CHECK ENGINE light stays on, the
vehicle should be taken to an authorized GM dealer as
soon as possible for service.
If the CHECK ENGINE
and REDUCED ENGINE
POWER lights are on, a
noticeable reduction in
the vehicle's performance
may occur.