GMC 1994 Yukon Owner's Manual page 122

Tachometer
If you have a
tachometer, it displays
the engine speed in
revolutions per minute
(rpm).
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.
Gages can indicate when there may be or is a problem with one of your
vehicle's functions. Often gages and warning lights work together to let you
know when there's a problem with your vehicle.
When one of the warning lights comes on and stays on when you are
driving, or when one of the gages shows there may be a problem, check the
section that tells you what to do about it. Please follow the manual's advice.
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