2018 GMC SIERRA brakes

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
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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 327
Fifth-wheel or gooseneck kingpin
weight should be 15 to 25% of the
trailer weight up to the maximum
amount specified in the trailering
chart for the vehicle. See“Weight of
the Trailer” underTrailer Towing
0 307.
The hitch should be located in the
pickup bed so that its centerline is
over or slightly in front of the rear
axle. Take care that it is not so far
forward that it will contact the back
of the cab in sharp turns. This is
especially important for short box
pickups. Trailer pin box extensions
and sliding fifth-wheel hitch
assemblies can help this condition.
There should be at least 15 cm (6 in)
of clearance between the top of the
pickup box and the bottom of the
trailer shelf that extends over
the box.
Safety Chains
Always attach chains between the
vehicle and the trailer. Cross the
safety chains under the tongue of
the trailer to help prevent the tongue
from contacting the road if it becomes separated from the hitch.
Instructions about safety chains
may be provided by the hitch
manufacturer or by the trailer
manufacturer. If the trailer is being
towed with a factory-installed step
bumper, safety chains may be
attached to the attaching points on
the bumper; otherwise, safety
chains should be attached to holes
on the trailer hitch platform. Always
leave just enough slack so the
combination can turn. Never allow
safety chains to drag on the ground.
Trailer Brakes
A loaded trailer that weighs 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.
State and local regulations may also
require the trailer to have its own
braking system if loaded above a
certain threshold. These
requirements vary from state to
state.
Read and follow the instructions for
the trailer brakes so they are
installed, adjusted, and maintained
properly.
Do not tap into the vehicle's
hydraulic brake system.
Auxiliary Battery
The auxiliary battery provision can
be used to supply electrical power
to additional equipment that may be
added, such as a slide-in camper.
If equipped, this relay will be on the
driver side of the vehicle, next to the
underhood electrical center.
Be sure to follow the proper
installation instructions included with
any electrical equipment that is
installed.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
328 Driving and Operating
Caution
Leaving electrical equipment on
for extended periods will drain the
battery. Always turn off electrical
equipment when not in use and
do not use equipment that
exceeds the maximum amperage
rating of 30 amps for the auxiliary
battery provision.
Trailer Wiring Harness
The vehicle is equipped with one of
the following wiring harnesses for
towing a trailer or hauling a slide-in
camper.
Basic Trailer Wiring
All regular, double cab, and crew
cab pickups have a seven-wire
trailer towing harness.
For vehicles not equipped with
heavy-duty trailering, the harness is
secured to the vehicle's frame
behind the spare tire mount. The
harness requires the installation of a
trailer connector, which is available
through your dealer.Use only a round, seven-wire
connector with flat blade terminals
meeting SAE J2863 specifications
for proper electrical connectivity.
The seven-wire harness contains
the following trailer circuits:
.
Green/Violet: Right Stop/Turn
Signal
. Yellow/Gray: Left Stop/Turn
Signal
. Gray/Brown: Taillamps/Parking
Lamps
. White/Green: Back-up Lamps
. Red/Green: Battery Feed
. White: Ground
. Blue: Electric Trailer Brake
The fuse for the electric trailer brake
circuit is installed in the underhood
electrical center, but the wires may
not be connected. They should be
connected by your dealer or a
qualified service center. To control
electric trailer brakes, a trailer brake
controller needs to be installed on
the vehicle by your dealer or a qualified service center, see
“Electric Brake Control Wiring
Provisions”
later in this section.
Heavy-Duty Trailer Wiring Harness
Package
For vehicles equipped with
heavy-duty trailering, the harness
connector is mounted in the bumper.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 329
For vehicles with the fifth wheel/
gooseneck trailer package, the
harness connector is mounted on
the inside of the pickup bed behind
the rear wheel.
The seven-wire harness contains
the following trailer circuits:
.Green/Violet: Right Stop/Turn
Signal
. Yellow/Gray: Left Stop/Turn
Signal
. Gray/Brown: Taillamps/Parking
Lamps
. White/Green: Back-up Lamps
. Red/Green: Battery Feed .
White: Ground
. Blue: Electric Trailer Brake
To help charge a remote
(non-vehicle) battery, press the Tow/
Haul Mode button at the end of the
shift lever. If the trailer is too light for
Tow/Haul Mode, turn on the
headlamps to help charge the
battery.
Camper/Fifth-Wheel Trailer Wiring
Package
For vehicles without the fifth wheel/
gooseneck trailer package,
seven-wire camper harness is under
the rear bumper, attached to the
frame near the rear crossmember.
A connector must be added to the
wiring harness that connects to the
camper.
The harness contains the following
camper/trailer circuits:
. Green/Violet: Right Stop/Turn
Signal
. Yellow/Gray: Left Stop/Turn
Signal .
Gray/Brown: Taillamps/Parking
Lamps
. White/Green: Back-up Lamps
. Red/Green: Battery Feed
. White: Ground
. Blue: Electric Trailer Brake
If the vehicle is equipped with the
heavy-duty trailering option, see
“Heavy-Duty Trailer Wiring Harness
Package” earlier in this section.Electric Brake Control Wiring
Provisions
Wiring provisions for an electric
trailer brake controller are included
with the vehicle as part of the trailer
wiring package. The instrument
panel contains blunt cut wires above
the parking brake assembly for the
electric trailer brake controller.
The harness contains the following
circuits:
.
Blue: Electric Trailer Brakes
. Red/Black or Red/Blue:
Battery Feed
. White/Blue: Brake Apply Signal