GMC Sierra 2015 Owner's Manual page 464

7. Shift the transmission to
P (Park) and turn off the ignition.
8. Disconnect the vehicle from the
tow vehicle.
9. Release the parking brake.
10. Reset any lost presets.
The outside temperature
display will default to 0 °C
(32 °F) but will reset with
normal usage.
Dolly Towing
Front Towing (Front Wheels Off
the Ground) Two-Wheel-Drive
Vehicles
Vehicle Care
Caution
If a two-wheel-drive vehicle is
towed with the rear wheels on the
ground, the transmission could be
damaged. The repairs would not
be covered by the vehicle
warranty. Never tow the vehicle
with the rear wheels on the
ground.
Two-wheel-drive vehicles should not
be towed with the rear wheels on
the ground. Two-wheel-drive
transmissions have no provisions
for internal lubrication while being
towed.
To dolly tow a two-wheel-drive
vehicle, the vehicle must be towed
with the rear wheels on the dolly.
See Rear Towing (Rear Wheels Off
the Ground) later in this section.
10-97