Chevrolet 2009 Suburban Owner's Manual page 133

A (LOCK/OFF): This position locks the ignition. It also
locks the transmission on automatic transmission
vehicles. The key can be removed in LOCK/OFF.
On vehicles with an automatic transmission, the shift
lever must be in P (Park) to turn the ignition switch
to LOCK/OFF.
The steering can bind 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 doesn't work, then the vehicle needs service.
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.
B (ACC/ACCESSORY): This position lets things like
the radio and the windshield wipers operate while
the engine is off. Use this position if the vehicle must
be pushed or towed.
C (ON/RUN): This position can be used to operate the
electrical accessories and to display some instrument
panel cluster warning and indicator lights. The switch
stays in this position when the engine is running.
The transmission is also unlocked in this position
on automatic transmission vehicles.
If you leave the key in the ACC/ACCESSORY or ON/
RUN position with the engine off, the battery could be
drained. You may not be able to start the vehicle if the
battery is allowed to drain for an extended period of time.
D (START): This is the position that starts the engine.
When the engine starts, release the key. The ignition
switch returns to ON/RUN for driving.
A warning tone will sound when the driver door is
opened, the ignition is in ACC/ACCESSORY or
LOCK/OFF and the key is in the ignition.
2-27