GMC 2010 Yukon/Yukon XL Owner's Manual page 226

The lever on the left side of the steering column
includes the following:
Turn and Lane Change Signals
Headlamp High/Low-Beam Changer
Windshield Wipers
Windshield Washer
Rear Wiper Delay
Rear Wiper
Rear Wiper Wash
Flash-to-Pass.
Information for these features is on the pages following.
4-4
Move the lever all the way up or down to signal a turn.
Raise or lower the lever for less than one second until
the arrow starts to flash to signal a lane change. This
causes the turn signals to automatically flash three
times. It will flash six times if tow-haul mode is active.
Holding the turn signal lever for more than one second
will cause the turn signals to flash until you release the
lever.
The lever returns to its starting position whenever it is
released.
If after signaling a turn or a lane change the arrows
flash rapidly or do not come on, a signal bulb could be
burned out.
Have the bulbs replaced. If the bulb is not burned out,
check the fuse. See Fuses and Circuit Breakers on
page 6 118.
An arrow on the
instrument panel cluster
flashes in the direction of
the turn or lane change.