GMC 1996 Sonoma Owner's Manual page 69

An indicator light near the lever shows you the transfer
case settings:
0
2HI
4HI
N
SET PARK BRAKE
4LO
The front axle portion of the diagram on the indicator
will light up when you shift into four-wheel drive. A
slight delay between shifting and the pattern's lighting is
normal. If the pattern does not light up, or if the
front axle lights do not go out after you shift out of
four-wheel drive, have your dealer check your system.
Turn the INT
LIGHTS switch located
to
the right
of your headlamp switch to dim your transfer case
indicator light when your headlamps or parking lamps
are on. This will also cause your instrument panel lights
to dim.
2H1: This setting is for driving in most street and
highway situations. Your front axle is not engaged in
two-wheel drive.
4HI: This setting engages your front axle to help
drive your vehicle. Use 4HI when you need extra
traction, such as on snowy or icy roads, or in most
off-road situations.
N SET PARK BRAKE: Shift to this neutral setting
only when your vehicle needs to be towed.
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