GMC 1999 Sierra 1500 Pickup Owner's Manual page 126

Features & Controls
Cargo Lamp
To turn your optional cargo lamp on, push the side of the switch with the
cargo lamp symbol on it. The switch is below the main light switch. The
dome light must be on for the cargo lamp to work.
Underhood Reel Light
K2255
You may have an underhood reel light.
If
you do
it
is located inside the
engine compartment on the passenger side fender. You can use
it
as a
flashlight.
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