GMC 1996 Sierra Owner's Manual page 127

Have you recently changed brands of fuel?
If so, be sure to fuel your vehicle with quality fuel (see
"Fuel" in the Index). Poor fuel quality will cause your
engine not to run as efficiently as designed. You may
notice this as stalling after start-up, stalling when you
put the vehicle into gear, misfiring, hesitaIion on
acceleration or stumbling on acceleration. (These
conditions may go away once the engine is warmed up.)
This will be detected by the system and cause the light
to turn on.
If you experience this condition, change the fuel brand
you use. It will require at least one full tank of the
proper fuel to turn the light off.
If none of the above steps have made the light turn off,
have your dealer or qualified service center check the'
vehicle. Your dealer has the proper test equipment and
diagnostic tools to fix any mechanical or electrical
problems
that
may have developed.
Oil Pressure Gage
0
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80
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 Wa (kilopascals).
Oil pressure may vary with engine speed, outside
temperature and oil viscosity, but readings above the
low pressure zone indicate the normal operating range.
A reading in the low pressure zone may be caused
by a dangerously low oil level or some other problem
causing low oil pressure. Check your oil as soon
as possible.