GMC SIERRA 1994 Manual page 127

To reset the trip odometer, fully press the reset button located near the trip
odometer readout. If the reset button is not fully pressed, the trip odometer
may not go all the way back to zero. If it doesn't, you may have to press the
reset button again to reset the readout to zero.
Tachometer
If you have a
tachometer, it displays
the engine speed in
revolutions per minute
(rpm).
I
NOTICE:
Do not operate the engine with the tachometer in the red area,
your engine or other parts could be damaged.
Damage to your engine or vehicle caused by operating the
engine in the red area isn't covered by your vehicle warranty.
Warning Lights and Indicators
This section describes the warning lights and gages that may be on your
vehicle. The pictures will help you locate them.
Warning lights and gages can signal that something is wrong before it
becomes serious enough to cause an expensive repair or replacement.
Paying attention to your warning lights and gages could also save you or
others from injury.
Warning lights go on when there may be or is a problem with one of your
vehicle's functions. As you will see in the details on the next few pages,
some warning lights come on briefly when you turn the ignition key just to
let you know they're working. If you are familiar with this section, you
should not be alarmed when this happens.
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