GMC Sierra 2018 Owner's Manual page 419

418 Vehicle Care
6. 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.
7. Shift the transmission to
P (Park).
Caution
If the steering column is locked,
vehicle damage may occur.
8. Move the steering wheel to
make sure the steering column
is unlocked.
9. 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 turn the ignition
key off.
3. Connect the battery.
4. Apply the brake pedal.
5. Turn the ignition on 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 0 262.
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.
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