Parked; Running The Vehicle While Parked; Automatic Transmission - GMC Sierra 2018 Owner's Manual

Warning (Continued)
There are holes or openings
in the vehicle body from
damage or aftermarket
modifications that are not
completely sealed.
If unusual fumes are detected or
if it is suspected that exhaust is
coming into the vehicle:
Drive it only with the
windows completely down.
Have the vehicle repaired
immediately.
Never park the vehicle with the
engine running in an enclosed
area such as a garage or a
building that has no fresh air
ventilation.
Running the Vehicle
While Parked
It is better not to park with the
engine running.
If the vehicle is left with the engine
running, follow the proper steps to
be sure the vehicle will not move.
See Shifting Into Park 0 252 and
Engine Exhaust 0 254.
If parking on a hill and pulling a
trailer, see Driving Characteristics
and Towing Tips 0 293.
Driving and Operating
Automatic
Transmission
If equipped, there is an electronic
shift lever position indicator within
the instrument cluster. This display
comes on when the ignition key is
turned to the on.
There are several different positions
for the shift lever.
Heavy-Duty 6-Speed Automatic
Transmission Shown, Others
Similar
See Range Selection Mode under
Manual Mode 0 258.
P : This position locks the rear
wheels. Use P (Park) when starting
the engine because the vehicle
cannot move easily.
255