GMC 2015 Sierra Owner's Manual page 305

9-42 Driving and Operating
Electronic Transfer Case
Use the transfer case knob, next to
the steering wheel, to shift into and
out of four-wheel drive for extra
traction.
Indicator lights on the knob show
which setting the transfer case is in.
The N (Neutral) indicator is on the
face of the knob. The indicator lights
display briefly when the ignition is
turned on, and one will stay on.
If the lights display momentarily
when the ignition is in ON/RUN, but
none stay on, the knob may have
been turned while the vehicle was
off. To see the indicator, turn the
knob to another position so that it
matches the actual transfer case
setting. If no lights display, take the
vehicle to your dealer for service.
An indicator light flashes while
shifting and until the shift is
complete.
If the transfer case cannot complete
a requested shift, it will return to the
last chosen setting. Turn the control
back to the previous setting to see
the indicator light.
Caution
Shifting the transmission into gear
before the requested mode
indicator light has stopped
flashing could damage the
transfer case.
The settings are:
N (Neutral): Use only when the
vehicle needs to be towed. See
Recreational Vehicle Towing on
page 10-94 or Towing the Vehicle
on page 10-94.
2 (Two-Wheel Drive High): Use
for driving on most streets and
highways. The front axle is not
engaged. This setting provides the
best fuel economy.
4 (Four-Wheel Drive Low): This
setting engages the front axle and
delivers extra torque. Choose 4 if
driving off-road in deep sand, deep
mud, or deep snow, and while
climbing or descending steep hills.
When engaged, keep vehicle speed
below 72 km/h (45 mph).
Shifting into 4 will turn Traction
Control and StabiliTrak off. See
Traction Control/Electronic Stability
Control on page 9-50.