2012 GMC Sierra Owner's Manual - Page 72

3-4 Seats and Restraints Center Seat If equipped, the center front seatback doubles as an armrest and cupholder/storage area for the driver and passenger when the center front seat is not used. Do not use it as a seating position when the seatback is folded down. Power Seat Adjustment To adjust the seatback, see "Power Reclining Seatbacks" under Reclining Seatbacks on page 3‑5. Lumbar Adjustment Manual Lumbar To adjust a power seat, if equipped: . Move the seat forward or rearward by sliding the control forward or rearward. If available, raise or lower the front or rear part of the seat cushion by moving the front or rear of the control up or down. If available, raise or lower the entire seat by moving the entire control up or down. If equipped, increase or decrease manual lumbar support by turning the knob forward or rearward. . .