GMC 2003 GMT560 T-Series, Owner'S Manual, Page: 96 / 284

Malfunction Indicator Lamp
Service Engine Soon Light
If this light comes on or
flashes while you are
driving, two things may
happen.
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 doesn’t come on at all, have it repaired.
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 engine oil pressure gage, on the lower right portion
of your instrument panel cluster, shows engine oil
pressure in psi (pounds per square inch) or in kPa
(kilopascals). Oil pressure may vary with outside
temperature and oil viscosity, but readings of
30 to 40 psi (205 to 275 kPa) on gasoline engines at
operating temperature and moderate road speeds
are normal. If you have a diesel engine, the normal
operating range should be between 35 and 70 psi
(240 to 480 kPa).
A reading in the low pressure zone may be caused by a
dangerously low oil level or other problem.
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