2012 GMC Sierra Owner's Manual - Page 73

Seats and Restraints Power Lumbar To raise or lower the height of the support, press and hold the top or bottom of the control. 3-5 WARNING (Continued) For proper protection when the vehicle is in motion, have the seatback upright. Then sit well back in the seat and wear the safety belt properly. Reclining Seatbacks { WARNING Sitting in a reclined position when the vehicle is in motion can be dangerous. Even when buckled up, the safety belts cannot do their job. To adjust the power lumbar support, if equipped: . On vehicles with two-way lumbar, press and hold the top or bottom of the control to increase or decrease lumbar support. On vehicles with four-way lumbar, press and hold the front or rear of the control to increase or decrease lumbar support. The shoulder belt will not be against your body. Instead, it will be in front of you. In a crash, you could go into it, receiving neck or other injuries. The lap belt could go up over your abdomen. The belt forces would be there, not at your pelvic bones. This could cause serious internal injuries. (Continued) . Do not have a seatback reclined if the vehicle is moving.