GMC 2003 Sonoma Owner's Manual page 13

Reclining Seatbacks
To adjust a manual
seatback, lift the lever on
the outboard side of
the seat.
Release the lever to lock the seatback where you want
it. To return the seat to an upright position, pull up
on the lever without pushing on the seatback.
If your vehicle is equipped with the vertical power seat
control described in Power Seats
on
page 1-4,
pressing it rearward allows the seatback to recline.
But don't have a seatback reclined if your vehicle is
moving.
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