GMC C series 2002 Owner's Manual page 12

Height Adjustment
To adjust the height of air
on the front outboard side of the seat. Push the knob to
inflate. Pull the knob to deflate.
To adjust the height of
-
a self contained seat
-
(hand pumped air seat),
push the seat height
adjustment pump lever,
located on the lower
outboard side, down and
continue pumping to raise
the seat. Press the lever and
hold it to lower the seat.
-
sourced seats, use the knob
Lumbar Adjustments
To adjust the height of the
cushion, lift the cushion
height adjustment handle
up and forward. You can
choose between two
settings. The handle is
located underneath the
seat, in the front.
To get more support in the
lumbar area of your back,
turn the lumbar adjustment
knob. The knob is located
on the upper cushion,
on the inboard side of
the driver's seat and the
outboard side of the
passenger's seat.
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