1997 GMC Sonoma Owner's Manual - Page 11

Manual Lumbar Support (Option) If you have this feature, there will be a knob the on outside of the driver and passenger bucket seats. Reclining Seatbacks (Bucket Seats or 60/40~Bench) To adjust the front seatback, lift the lever on the outer side of the seat. Turn the knob counterclockwise to increase lumbar support and clockwise to decrease lumbar support. Release the lever to lock seatback where you want it. the and Pull up on the lever the seat will go toan upright position. 1-3