2012 GMC Sierra Owner's Manual - Page 423

Vehicle Care 10-37 Headlamp Aiming The vehicle has a visual optical headlamp aiming system. The aim of the headlamps has been preset at the factory and should need no further adjustment. However, if the vehicle is damaged in a crash, the aim of the headlamps may be affected and adjustment may be necessary. If oncoming vehicles flash their high beams at you, this may mean the vertical aim of the headlamps needs to be adjusted. It is recommended that the vehicle be taken to the dealer for service if the headlamps need to be adjusted. It is possible, however, to re-aim the headlamps as described. The vehicle should: . Be placed so the headlamps are 7.6 m (25 ft) from a light‐colored wall. Have all four tires on a level surface which is level all the way to the wall. Be placed so it is perpendicular to the wall. Not have any snow, ice, or mud on it. Be fully assembled and all other work stopped while headlamp aiming is being performed. Be loaded with a full tank of fuel and one person or 75 kg (160 lbs) sitting on the driver seat. Have the tires properly inflated. Have the spare tire in its proper location in the vehicle. . 3. Install the new blade onto the arm connector and make sure the grooved areas are fully set in the locked position. For the proper type and size, see Maintenance Replacement Parts on page 11‑15. . . . Glass Replacement If the windshield or front side glass must be replaced, see your dealer to determine the correct replacement glass. . . .