GMC Sierra 2015 Owner's Manual page 463

10-96 Vehicle Care
4. Shift the transfer case to
N (Neutral). See Shifting into
N (Neutral) under Four-Wheel
Drive on page 9-39. Check that
the vehicle is in N (Neutral) by
shifting the transmission to
R (Reverse) and then to D
(Drive). There should be no
movement of the vehicle while
shifting.
5. Shift the transmission into D
(Drive). Turn the engine off.
Then shift the transmission into
P (Park).
6. Wait for at least 10 seconds,
then restart the engine.
7. Shift the transmission to D
(Drive), then turn the engine off
again.
Caution
Failure to disconnect the negative
battery cable or to have it contact
the terminals can cause damage
to the vehicle.
8. Disconnect the negative battery
cable at the battery and secure
the nut and bolt. Cover the
negative battery post with a
non-conductive material to
prevent any contact with the
negative battery terminal.
9. Shift the transmission to
P (Park).
Caution
If the steering column is locked,
vehicle damage may occur.
10. Move the steering wheel to
make sure the steering column
is unlocked.
11. With a foot on the brake pedal,
release the parking brake.
Keep the ignition key in the
towed vehicle in ACC/
ACCESSORY to prevent the
steering column from locking.
Disconnecting the Towed Vehicle
Before disconnecting the towed
vehicle:
1. Park on a level surface.
2. Set the parking brake, then shift
the transmission to P (Park), and
move the ignition key to OFF.
3. Connect the battery.
4. Apply the brake pedal.
5. Turn the ignition to ON/RUN with
the engine off. Shift the transfer
case out of N (Neutral) to
Two-Wheel Drive High. See
Shifting out of N (Neutral)
under Four-Wheel Drive on
page 9-39. See your dealer if the
transfer case cannot be shifted
out of N (Neutral).
6. Check that the vehicle is in
Two-Wheel Drive High by
shifting the transmission to
R (Reverse) and then to D
(Drive). There should be
movement of the vehicle while
shifting.