GMC Sierra 2000 Owner's Manual page 141

Malfunction Indicator Lamp (Service
Engine Soon Light) (7.4L Gasoline Engine
on Complete Vehicle Over 14,000 GVWR
and Chassis Cabs)
First, you won't notice any difference in engine
performance, but your tail pipe emissions may increase.
Second, your engine may not run properly or may stall
without warning. If either of these things happen, drive
or tow your vehicle to your dealer for service.
This light should come on when the ignition is on, but
the engine is not running, as a check to show you it is
working. If it does not come on at all, have it repaired.
If this light comes on
or flashes while you
are driving, two things
may happen.
NOTICE:
If you keep driving your vehicle with this light
on, after a while, your emission controls may not
work as well, your fuel economy may not be as
good and your engine may not run as smoothly.
This could lead to costly repairs that may not be
covered by your warranty.
Oil Pressure Gage
The oil pressure gage shows
the engine oil pressure in
psi (pounds per square inch)
when the engine is
running. Canadian vehicles
indicate pressure in
kPa (kilopascals).
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