GMC 2010 Yukon/Yukon XL Owner's Manual page 225

located on top of the steering column, to make the front
and rear turn signal lamps flash on and off. This warns
others that you are having trouble. Press again to turn
the flashers off.
When the hazard warning flashers are on, the vehicle's
turn signals will not work.
To sound the horn, press the center pad on the steering
wheel.
Press this button
The tilt lever is located on the lower left side of the
steering column.
To adjust the steering wheel:
1. Hold the steering wheel and pull the lever.
2. Move the steering wheel to a comfortable position.
3. Release the lever to lock the wheel in place.
Do not adjust the steering wheel while driving.
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