GMC 2000 Sonoma Owner's Manual page 86

Shift Light
This light will show you when to shift to the next higher
gear for best fuel economy.
When this light comes on, you can shift to the next
higher gear if weather, road and traffic conditions let
you. For the best fuel economy, accelerate slowly and
shift when the light comes on.
While you accelerate, it is normal for the light to go on
and off if you quickly change the position of the
accelerator. Ignore the SHIFT light when you downshift.
CAUTION:
If you skip a gear when you downshift, you could
lose control of your vehicle. You could injure
yourself or others. Don't shift down more than
one gear at a time when you downshift.
If you have a manual
transmission, you have a
SHIFT light.
Four Wheel Drive (If Equipped)
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If your vehicle has four wheel drive, you can send your
engine's driving power to all four wheels for extra
traction. To get the most satisfaction out of four
drive, you must be familiar with its operation. Read the
part that follows before using four
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should use two wheel drive (2HI) for most normal
driving conditions.
NOTICE:
Driving in the 4HI or 4LO positions for a long
time on dry or wet pavement could shorten the
life of your vehicle's drivetrain.
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wheel
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wheel drive. You
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