towing GMC SIERRA 2018 Owner's Guide

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 277
Shifting Out of N (Neutral)
To shift:1. Set the parking brake and apply the brake pedal.
2. Turn the ignition on with the engine off.
3. Shift the transmission to N (Neutral).
4. Turn the transfer case knob to 2
m.
After the transfer case has
shifted out of N (Neutral), the
N (Neutral) light will go out.
5. Release the parking brake.
Caution
Shifting the transmission into gear
before the requested mode
indicator light has stopped
flashing could damage the
transfer case.
6. Start the engine and shift the transmission to the
desired gear.
Automatic Transfer Case
If equipped, use the transfer case
knob next to the steering wheel to
shift into and out of four-wheel drive.
All of the lights will blink on then off
momentarily when the ignition is
turned on. The light that remains on
will indicate the state of the
transfer case.
If the indicator mark on the switch
does not match up with the light
then that likely means the switch
was moved when the ignition
was off. The indicator mark on the switch
must line up with the indicator light
before a shift can be commanded.
To command a shift rotate the
transfer case switch to the new
desired position. The light will blink
meaning that the shift is in progress.
When the shift is completed the new
position will be illuminated. If the
transfer case can not complete a
shift command, it will go back to its
last chosen setting.
The settings are:
N (Neutral) :
Use only when the
vehicle needs to be towed. See
Recreational Vehicle Towing 0430
or Towing the Vehicle 0430.
2
m(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.
AUTO (Automatic Four-Wheel
Drive) : Use when road surface
traction conditions are variable.
When driving in AUTO, the front
axle is engaged, and the vehicle's
power is sent to the front and rear

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 279
Shifting Out of 4n
To shift:1. The vehicle must be stopped or moving less than 5 km/h
(3 mph) with the transmission
in N (Neutral) and the ignition
on. It is best for the vehicle to
be moving 1.6 to 3.2 km/h
(1 to 2 mph).
2. Turn the knob to 4
m, AUTO,
or 2
m. Wait for the 4m, AUTO,
or 2
mindicator light to stop
flashing before shifting the
transmission into gear.
Caution
Shifting the transmission into gear
before the requested mode
indicator light has stopped
flashing could damage the
transfer case. If the transmission is in gear and/or
moving more than 5 km/h (3 mph),
the 4
m, AUTO, or 2mindicator light
will flash for 30 seconds but will not
complete the shift. With the vehicle
moving less than 5 km/h (3 mph),
and the transmission in N (Neutral),
attempt the shift again.
Shifting Into N (Neutral)
To shift into N (Neutral):
1. Park the vehicle on a level surface.
2. Set the parking brake and press and hold the brake
pedal. See Parking Brake
0 281.
3. Start the vehicle or turn the ignition on.
4. Shift the transmission to N (Neutral).
5. Shift the transfer case to 2
m. 6. Turn the transfer case knob
clockwise to N (Neutral) until it
stops and hold it there until the
N (Neutral) light starts blinking.
This will take at least
10 seconds. Then slowly
release the knob to the 4
n
position. The N (Neutral) light
will come on when the transfer
case shift to N (Neutral) is
complete.
7. With the engine running, verify that the transfer case is in
N (Neutral) by shifting the
transmission to R (Reverse),
then shift the transmission to
D (Drive). There should be no
movement of the vehicle while
shifting the transmission.
8. Turn the engine off, and the ignition to ACC/ACCESSORY.
9. Place the transmission shift lever in P (Park). See
Recreational Vehicle Towing
0430.
10. Turn the ignition to off.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 291
{Warning
The Parking Assist system does
not detect children, pedestrians,
bicyclists, animals, or objects
located below the bumper or that
are too close or too far from the
vehicle. It is not available at
speeds greater than 8 km/h
(5 mph). To prevent injury, death,
or vehicle damage, even with
Parking Assist, always check the
area around the vehicle and
check all mirrors before moving
forward or backing.
The instrument cluster may have a
parking assist display with bars that
show“distance to object” and object
location information for the Parking
Assist system. As the object gets
closer, more bars light up and the
bars change color from yellow to
amber to red.
When an object is first detected in
the rear, one beep will be heard
from the rear, or both sides of the
Safety Alert Seat will pulse two
times. When an object is very close
(<0.6 m (2 ft) in the vehicle rear,
or <0.3 m (1 ft) in the vehicle front),
a continuous beep will sound from
the front or rear, or both sides of the Safety Alert Seat will pulse five
times. Beeps for FPA are higher
pitched than for RPA.
Turning the Features On or Off
PressXon the center stack to
turn the Front and Rear Parking
Assist on or off. The indicator light in
the button comes on when the
features are on and turns off when
the features have been disabled.
Front and Rear Parking Assist can
be turned off, on, or on with towbar
through vehicle personalization. See
“Park Assist” underVehicle
Personalization 0165. If the parking
assist is turned off through vehicle
personalization, the parking assist
button on the center stack will be
disabled. To turn the parking assist
on again, select On in vehicle
personalization. The On with Towbar
setting allows for the parking assist
to work properly with an attached
trailer hitch. Turn off parking assist
when towing a trailer.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 295
Warning (Continued)
Complete attention is always
required while driving, and you
should be ready to take action
and apply the brakes and/or steer
the vehicle to avoid crashes.
FAB may slow the vehicle to a
complete stop to try to avoid a
potential crash. The vehicle will only
hold at a stop briefly. A firm press of
the accelerator pedal will
release FAB.
{Warning
FAB may automatically brake the
vehicle suddenly in situations
where it is unexpected and
undesired. It could respond to a
turning vehicle ahead, guardrails,
signs, and other non-moving
objects. To override FAB, firmly
press the accelerator pedal, if it is
safe to do so.
Intelligent Brake Assist (IBA)
IBA may activate when the brake
pedal is applied quickly by providing
a boost to braking based on the
speed of approach and distance to
a vehicle ahead.
Minor brake pedal pulsations or
pedal movement during this time is
normal and the brake pedal should
continue to be applied as needed.
IBA will automatically disengage
only when the brake pedal is
released.
{Warning
IBA may increase vehicle braking
in situations when it may not be
necessary. You could block the
flow of traffic. If this occurs, take
your foot off the brake pedal and
then apply the brakes as needed.
FAB and IBA can be disabled
through vehicle personalization. See
“Collision/Detection Systems” under
Vehicle Personalization 0165.
{Warning
Using FAB or IBA while towing a
trailer could cause you to lose
control of the vehicle and crash.
Turn the system to Alert or Off
when towing a trailer.
Lane Departure Warning
(LDW) (2500/3500 Series)
If equipped, LDW may help avoid
crashes due to unintentional lane
departures. It may provide an alert if
the vehicle is crossing a lane
marking without using a turn signal
in that direction. LDW uses a
camera sensor to detect the lane
markings at speeds of 56 km/h
(35 mph) or greater.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 297
markings, or other road
imperfections. This is normal system
operation; the vehicle does not need
service. Turn LDW off if these
conditions continue.
Lane Keep Assist (LKA)
(1500 Series)
If equipped, LKA may help avoid
crashes due to unintentional lane
departures. It may assist by gently
turning the steering wheel if the
vehicle approaches a detected lane
marking without using a turn signal
in that direction. It may also provide
a Lane Departure Warning (LDW)
system alert as the lane marking is
crossed. The LKA system will not
assist or provide an LDW alert if it
detects that you are actively
steering. Override LKA by turning
the steering wheel. LKA uses a
camera to detect lane markings
between 60 km/h (37 mph) and
180 km/h (112 mph).
{Warning
The LKA system does not
continuously steer the vehicle.
It may not keep the vehicle in the
lane or give a Lane Departure
Warning (LDW) alert, even if a
lane marking is detected.
The LKA and LDW systems
may not:. Provide an alert or enough
steering assist to avoid a
lane departure or crash.
. Detect lane markings under
poor weather or visibility
conditions. This can occur if
the windshield or
headlamps are blocked by
dirt, snow, or ice, if they are
not in proper condition, or if
the sun shines directly into
the camera.
. Detect road edges.
. Detect lanes on winding or
hilly roads.
(Continued)
Warning (Continued)
If LKA only detects lane markings
on one side of the road, it will
only assist or provide an LDW
alert when approaching the lane
on the side where it has detected
a lane marking. Even with LKA
and LDW, you must steer the
vehicle. Always keep your
attention on the road and
maintain proper vehicle position
within the lane, or vehicle
damage, injury, or death could
occur. Always keep the
windshield, headlamps, and
camera sensors clean and in
good repair. Do not use LKA in
bad weather conditions.
{Warning
Using LKA while towing a trailer
or on slippery roads could cause
loss of control of the vehicle and
a crash. Turn the system off.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 303
{Warning
Attempting to refuel without using
the funnel adapter may cause fuel
spillage and damage the capless
fuel system. This could cause a
fire and you or others could be
badly burned and the vehicle
could be damaged.
3. Remove and clean the funnel adapter and return to the
storage location.
Filling a Portable Fuel
Container
{Warning
Filling a portable fuel container
while it is in the vehicle can cause
fuel vapors that can ignite either
by static electricity or other
means. You or others could be
badly burned and the vehicle
could be damaged. Always:
(Continued)
Warning (Continued)
.Use approved fuel
containers.
. Remove the container from
the vehicle, trunk, or pickup
bed before filling.
. Place the container on the
ground.
. Place the nozzle inside the
fill opening of the container
before dispensing fuel, and
keep it in contact with the fill
opening until filling is
complete.
. Fill the container no more
than 95% full to allow for
expansion.
. Do not smoke, light
matches, or use lighters
while pumping fuel.
. Avoid using cell phones or
other electronic devices.
Trailer Towing
General Towing
Information
Only use towing equipment that has
been designed for the vehicle.
Contact your dealer or trailering
dealer for assistance with preparing
the vehicle for towing a trailer. Read
the entire section before towing a
trailer.
For towing a disabled vehicle, see
Towing the Vehicle 0430. For
towing the vehicle behind another
vehicle such as a motor home, see
Recreational Vehicle Towing 0430.
Driving Characteristics
and Towing Tips
Driving with a Trailer
When towing a trailer:
.
Become familiar with the state
and local laws that apply to
trailer towing.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
304 Driving and Operating
.The trailer must be equipped
with brakes adequate for the
intended use. A loaded trailer
weighing more than 900 kg
(2,000 lb) must be equipped with
its own brake system, with
brakes working on all axles.
Trailer braking equipment
conforming to Canadian
Standards Association (CSA)
requirement CAN3-D313, or its
equivalent, is recommended.
. Do not tow a trailer during the
first 800 km (500 mi) to prevent
damage to the engine, axle,
or other parts.
. Then during the first 800 km
(500 mi) of trailer towing, do not
drive over 80 km/h (50 mph) and
do not make starts at full throttle.
. The vehicle can tow in D (Drive)
but Manual Mode is
recommended. See Manual
Mode 0268. Use a lower gear if
the transmission shifts too often. .
Vehicles can tow in D (Drive).
The Tow/Haul Mode may be
used if the transmission shifts
too often. See Tow/Haul Mode
0 271.
. The Forward Automatic Braking
System should be set to Off
when towing. See Forward
Automatic Braking (FAB) 0294.
. Turn off Lane Keep Assist (LKA)
when towing.
{Warning
When towing a trailer, exhaust
gases may collect at the rear of
the vehicle and enter if the
liftgate, trunk/hatch, or rear-most
window is open.
When towing a trailer:
. Do not drive with the
liftgate, trunk/hatch,
or rear-most window open.
. Fully open the air outlets on
or under the instrument
panel.
(Continued)
Warning (Continued)
.Also adjust the climate
control system to a setting
that brings in only outside
air. See “Climate Control
Systems” in the Index.
For more information about
carbon monoxide, see Engine
Exhaust 0264.
Towing a trailer requires a certain
amount of experience. The
combination you are driving is
longer and not as responsive as the
vehicle itself. Get acquainted with
the handling and braking of the rig
before setting out for the open road.
The structure, tires, and brakes of
the trailer must be rated to carry the
load. Inadequate trailer equipment
can cause the combination to
operate in an unexpected or unsafe
manner.
Before starting, check all trailer hitch
parts and attachments, safety
chains, electrical connectors, lamps,

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 305
tires, and mirrors. Get familiar with
the handling and braking of the rig.
If the trailer has electric brakes, start
the combination moving and then
apply the trailer brake controller by
hand to be sure the brakes work.
During the trip, check occasionally
to be sure that the load is secure
and the lamps and any trailer
brakes still work.
Following Distance
Stay at least twice as far behind the
vehicle ahead as you would when
driving the vehicle without a trailer.
This can help to avoid heavy
braking and sudden turns.
Passing
More passing distance is needed
when towing a trailer. The
combination will not accelerate as
quickly and is longer so it is
necessary to go much farther
beyond the passed vehicle before
returning to the lane.
Backing Up
Hold the bottom of the steering
wheel with one hand. To move the
trailer to the left, move that hand to
the left. To move the trailer to the
right, move your hand to the right.
Always back up slowly and,
if possible, have someone
guide you.
Making TurnsCaution
Making very sharp turns while
trailering could cause the trailer to
come in contact with the vehicle.
The vehicle could be damaged.
Avoid making very sharp turns
while trailering.
When turning with a trailer, make
wider turns than normal. Do this so
the trailer will not strike soft
shoulders, curbs, road signs, trees,
or other objects. Avoid jerky or
sudden maneuvers. Signal well in
advance. If the trailer turn signal bulbs burn
out, the arrows on the instrument
cluster will still flash for turns. It is
important to check occasionally to
be sure the trailer bulbs are still
working.
Turn Signals When Towing a
Trailer
The turn signal indicators on the
instrument cluster flash whenever
signaling a turn or lane change.
Properly hooked up, the trailer
lamps also flash, telling other
drivers the vehicle is turning,
changing lanes, or stopping.
When towing a trailer, the arrows on
the instrument cluster flash for turns
even if the bulbs on the trailer are
burned out.
Check occasionally to be sure the
trailer bulbs are still working.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
306 Driving and Operating
Driving on Grades
Reduce speed and shift to a lower
gearbefore starting down a long or
steep downgrade. If the
transmission is not shifted down, the
brakes might get hot and no longer
work well.
Vehicles can tow in D (Drive). Shift
the transmission to a lower gear if
the transmission shifts too often
under heavy loads and/or hilly
conditions.
The Tow/Haul Mode may be used if
the transmission shifts too often.
See Tow/Haul Mode 0271.
When towing at high altitude on
steep uphill grades, consider the
following: Engine coolant will boil at
a lower temperature than at normal
altitudes. If the engine is turned off
immediately after towing at high
altitude on steep uphill grades, the
vehicle may show signs similar to
engine overheating. To avoid this,
let the engine run while parked,
preferably on level ground, with the
transmission in P (Park) for a few minutes before turning the engine
off. If the overheat warning comes
on, see
Engine Overheating 0363.
Parking on Hills
{Warning
Parking the vehicle on a hill with
the trailer attached can be
dangerous. If something goes
wrong, the rig could start to move.
People can be injured, and both
the vehicle and the trailer can be
damaged. When possible, always
park the rig on a flat surface.
If parking the rig on a hill: 1. Press the brake pedal, but do not shift into P (Park) yet. Turn
the wheels into the curb if
facing downhill or into traffic if
facing uphill.
2. Have someone place chocks under the trailer wheels. 3. When the wheel chocks are in
place, release the regular
brakes until the chocks absorb
the load.
4. Reapply the brake pedal. Then apply the parking brake and
shift into P (Park).
5. Release the brake pedal.
Leaving After Parking on a Hill
1. Apply and hold the brake pedal.
.Start the engine.
. Shift into a gear.
. Release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the chocks.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 307
Maintenance when Trailer
Towing
The vehicle needs service more
often when pulling a trailer. See
Maintenance Schedule0448.
Things that are especially important
in trailer operation are automatic
transmission fluid, engine oil, axle
lubricant, belts, cooling system, and
brake system. It is a good idea to
inspect these before and during
the trip.
Check periodically to see that all
hitch nuts and bolts are tight.
Engine Cooling When Trailer
Towing
The cooling system may temporarily
overheat during severe operating
conditions. See Engine Overheating
0 363.
Trailer Towing
If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
Do not tow a trailer during break-in.
See New Vehicle Break-In 0255.
{Warning
The driver can lose control when
pulling a trailer if the correct
equipment is not used or the
vehicle is not driven properly. For
example, if the trailer is too heavy
or the trailer brakes are
inadequate for the load, the
vehicle may not stop as expected.
The driver and passengers could
be seriously injured. The vehicle
may also be damaged; the
resulting repairs would not be
covered by the vehicle warranty.
Pull a trailer only if all the steps in
this section have been followed.
Ask your dealer for advice and
information about towing a trailer
with the vehicle.
Caution
Pulling a trailer improperly can
damage the vehicle and result in
costly repairs not covered by the
vehicle warranty. To pull a trailer
correctly, follow the advice in this
section and see your dealer for
important information about
towing a trailer with the vehicle.
See Vehicle Load Limits 0248 for
more information about the vehicle's
maximum load capacity.
To identify the trailering capacity of
the vehicle, read the information in
“Weight of the Trailer” later in this
section.
Trailering is different than just
driving the vehicle by itself.
Trailering means changes in
handling, acceleration, braking,
durability, and fuel economy.
Successful, safe trailering takes
correct equipment, and it has to be
used properly.