Cadillac 2010 DTS Owner's Manual page 131

The ignition switch has four different positions:
In order to shift out of P (Park), ignition must be in the
ON/RUN or ACC/ACCESSORY and the brake pedal
must be applied.
This is the only position in which the
ignition key can be inserted or removed. This position
locks the ignition and transmission and steering column.
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, the vehicle needs service.
and windshield wipers operate while the engine is off.
To use ACC/ACCESSORY, turn the key clockwise.
This position lets the radio
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