2011 GMC Acadia Owner's Manual - Page 358

10-30 Vehicle Care Headlamp Aiming Headlamp aim has been preset at the factory and should need no further adjustment. However, if your vehicle is damaged in a crash, the headlamp aim may be affected. Aim adjustment to the low-beam headlamps may be necessary if oncoming drivers flash their high-beam headlamps at you (for vertical aim). If the headlamps need to be re-aimed, it is recommended that you take the vehicle to your dealer for service. Bulb Replacement For the proper type of replacement bulbs, see Replacement Bulbs on page 10‑31. For any bulb‐changing procedure not listed in this section, contact your dealer. High Intensity Discharge (HID) Lighting { WARNING The low beam high intensity discharge lighting system operates at a very high voltage. If you try to service any of the system components, you could be seriously injured. Have your dealer or a qualified technician service them. The up‐level vehicle has HID headlamps. After an HID headlamp bulb has been replaced, the beam might be a slightly different shade than it was originally. This is normal. Halogen Bulbs { WARNING Halogen bulbs have pressurized gas inside and can burst if you drop or scratch the bulb. You or others could be injured. Be sure to read and follow the instructions on the bulb package.