2010 GMC Terrain Owner's Manual - Page 236

8-28 Driving and Operating To shift out of P (Park), turn the ignition to ON/RUN and apply the brake pedal. A (LOCK/OFF): This is the only position from which the key can be removed. This locks the steering wheel, ignition and automatic transmission. On vehicles with an automatic transmission, the shift lever must be in P (Park) to turn the ignition switch to the LOCK/OFF position. B (ACC/ACCESSORY): This position provides power to some of the electrical accessories. It unlocks the steering wheel and ignition. The transmission is also unlocked in this position on automatic transmission vehicles. To move the key from ACC/ACCESSORY to LOCK/OFF, push in the key and then turn it to LOCK/OFF. C (ON/RUN): The ignition switch stays in this position when the engine is running. This position can be used to operate the electrical accessories, including the ventilation fan and 12 volt power outlet, as well as to display some warning and indicator lights. Ignition Positions The ignition switch has four different positions. Notice: Using a tool to force the key to turn in the ignition could cause damage to the switch or break the key. Use the correct key, make sure it is all the way in, and turn it only with your hand. If the key cannot be turned by hand, see your dealer/retailer. The ignition switch can bind in the LOCK/OFF position with the wheels turned off center. If this happens, move the steering wheel from right to left while turning the key to ACC/ ACCESSORY. If this does not work, then the vehicle needs service.