brake GMC YUKON XL 2018 Repair Manual

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - crc - 6/21/17
250 Driving and Operating
{ WarningIBA 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 0 158 .
{ WarningUsing FAB or IBA while towing a
trailer could cause you to lose
control of the vehicle and crash.
Turn the system to Alert, or if the
vehicle has ACC to Off, when
towing a trailer.
A system unavailable message may
display if:
.
The front of the vehicle or
windshield is not clean. .
Heavy rain or snow is interfering
with object detection.
.
There is a problem with the
StabiliTrak system.
The FAB system does not need
service.
Side Blind Zone
Alert (SBZA) If equipped, the SBZA system is a
lane-changing aid that assists
drivers with avoiding crashes that
occur with moving vehicles in the
side blind zone (or spot) areas.
When the vehicle is in a forward
gear, the left or right side mirror
display will light up if a moving
vehicle is detected in that blind
zone. If the turn signal is activated
and a vehicle is also detected on
the same side, the display will flash
as an extra warning not to change
lanes. Since this system is part of
the Lane Change Alert (LCA)
system, read the entire LCA section
before using this feature. Lane Change Alert (LCA) If equipped, the LCA system is a
lane-changing aid that assists
drivers with avoiding lane change
crashes that occur with moving
vehicles in the side blind zone (or
spot) areas or with vehicles rapidly
approaching these areas from
behind. The LCA warning display
will light up in the corresponding
outside side mirror and will flash if
the turn signal is on.
{ WarningLCA does not alert the driver to
vehicles outside of the system
detection zones, pedestrians,
bicyclists, or animals. It may not
provide alerts when changing
lanes under all driving conditions.
Failure to use proper care when
changing lanes may result in
injury, death, or vehicle damage.
Before making a lane change,
always check mirrors, glance over
your shoulder, and use the turn
signals.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - crc - 6/21/17
Driving and Operating 259
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 0 355 . For
towing the vehicle behind another
vehicle such as a motor home, see
Recreational Vehicle Towing 0 355 .
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. These
requirements vary from state to
state. .
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.
.
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.
.
Do not use Adaptive Cruise
Control when towing. .
Turn off Parking Assist and Rear
Cross Traffic Alert (RTCA) when
towing.
.
The Forward Automatic Braking
System should be set to Off
when towing. See Forward
Automatic Braking (FAB) 0 21 .
.
Turn off Lane Keep Assist (LKA)
when towing. See Lane Keep
Assist (LKA) 0 252 .
{ WarningWhen 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)

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - crc - 6/21/17
260 Driving and Operating 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 0 215 .
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,
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 Turns
CautionMaking 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.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - crc - 6/21/17
Driving and Operating 261Driving on Grades Reduce speed and shift to a lower
gear before 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.
When towing, use the Tow/Haul
Mode to prevent damage to the
engine or transmission. See Tow/
Haul Mode 0 222 .
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 0 294 .
Parking on Hills
{ WarningParking 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.
2. Start the engine.
3. Shift into a gear.
4. Release the parking brake.
5. Let up on the brake pedal.
6. Drive slowly until the trailer is
clear of the chocks.
7. Stop and have someone pick
up and store the chocks.
Maintenance when Trailer
Towing
The vehicle needs service more
often when pulling a trailer. See
Maintenance Schedule 0 370 .
Things that are especially important
in trailer operation are automatic
transmission fluid, engine oil, axle
lubricant, belts, cooling system, and

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - crc - 6/21/17
262 Driving and Operating 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.
Trailer Towing Do not tow a trailer during break-in.
See New Vehicle Break-In 0 204 .
Before towing a trailer, see
"Hands-Free Operation" under
Liftgate 0 43 .
{ WarningThe 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
(Continued) Warning (Continued) 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.
CautionPulling 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. To identify the trailering capacity of
the vehicle, read the information in
“ Weight of the Trailer ” following.
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.
The following information has many
time-tested, important trailering tips
and safety rules. Many of these are
important for your safety and that of
your passengers. So please read
this section carefully before pulling a
trailer.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - crc - 6/21/17
268 Driving and Operating 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.
Be sure to read and follow the
instructions for the trailer brakes so
they are installed, adjusted, and
maintained properly. These
requirements vary from state to
state.
Do not tap into the vehicle's
hydraulic brake system.
Since the vehicle is equipped with
StabiliTrak, the trailer brakes cannot
tap into the vehicle's hydraulic
system. Trailer Wiring Harness The seven-pin trailer connector is
mounted in the bumper. This
connector can be plugged into a
seven-pin universal heavy-duty
trailer connector 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:
.
Yellow/Grey: Left Stop/Turn
Signal
.
Green/Violet: Right Stop/Turn
Signal
.
Grey/Brown: Taillamps
.
White: Ground
.
White/Green: Back-up Lamps
.
Red/Green: Battery Feed
.
Dark Blue: 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.
Electric Brake Control Wiring
Provisions These wiring provisions are
included with the vehicle as part of
the trailer wiring package. These
provisions are for an electric brake
controller.
The harness should be installed by
your dealer or a qualified service
center.
Tow/Haul Mode

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - crc - 6/21/17
Driving and Operating 269Pressing this button at the end of
the shift lever turns on and off the
Tow/Haul Mode.
This indicator light on the instrument
cluster comes on when the Tow/
Haul Mode is on.
Tow/Haul is a feature that assists
when pulling a heavy trailer or a
large or heavy load. See Tow/Haul
Mode 0 222 .
Tow/Haul is designed to be most
effective when the vehicle and
trailer combined weight is at least
75 % of the vehicle's Gross
Combined Weight Rating (GCWR).
See “ Weight of the Trailer ” under
Trailer Towing 0 262 . Tow/Haul is
most useful under the following
driving conditions:
.
When pulling a heavy trailer or a
large or heavy load through
rolling terrain. .
When pulling a heavy trailer or a
large or heavy load in
stop-and-go traffic.
.
When pulling a heavy trailer or a
large or heavy load in busy
parking lots where improved low
speed control of the vehicle is
desired.
Operating the vehicle in Tow/Haul
when lightly loaded or with no trailer
at all will not cause damage.
However, there is no benefit to the
selection of Tow/Haul when the
vehicle is unloaded. Such a
selection when unloaded may result
in unpleasant engine and
transmission driving characteristics
and reduced fuel economy. Tow/
Haul is recommended only when
pulling a heavy trailer or a large or
heavy load. Integrated Trailer Brake
Control System
The vehicle may have an Integrated
Trailer Brake Control (ITBC) system
for use with electric trailer brakes or
most electric-over-hydraulic trailer
brakes.
This symbol is on the Trailer Brake
Control Panel on vehicles with an
ITBC system. The power output to
the trailer brakes is based on the
amount of brake pressure being
applied by the vehicle ’ s brake
system, and on the type of trailer
brakes detected. This available
power output to the trailer brakes
can be adjusted to a wide range of
trailering situations.
The ITBC system is integrated with
the vehicle ’ s brake, antilock brake,
and StabiliTrak systems. In trailering
conditions that cause the vehicle ’ s

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - crc - 6/21/17
270 Driving and Operating antilock brake or StabiliTrak
systems to activate, power sent to
the trailer's brakes will be
automatically adjusted to minimize
trailer wheel lock-up. This does not
imply that the trailer has StabiliTrak.
If the vehicle ’ s brake, antilock brake,
or StabiliTrak systems are not
functioning properly, the ITBC
system may not be fully functional
or may not function at all. Make sure
all of these systems are fully
operational to ensure full
functionality of the ITBC system.
The ITBC system is powered
through the vehicle's electrical
system. Turning the ignition off will
also turn off the ITBC system. The
ITBC system is fully functional only
when the ignition is in on.
{ Warning
Connecting a trailer that has an
air brake system may result in
reduced or complete loss of trailer
braking. There may be an
increase in stopping distance or
(Continued) Warning (Continued) trailer instability which could
result in personal injury or
damage to the vehicle, trailer,
or other property. Use the ITBC
system only with electric or
electric over hydraulic trailer
brakes.
Trailer Brake Control Panel
1. Manual Trailer Brake Apply
Lever
2. Trailer Gain Adjustment
Buttons The ITBC system has a control
panel on the instrument panel to the
left of the steering column. The
control panel allows adjustment to
the amount of output, referred to as
Trailer Gain, available to the trailer
brakes and allows manual
application of the trailer brakes. The
Trailer Brake Control Panel is used
along with the Trailer Brake Display
Page on the DIC to adjust and
display power output to the trailer
brakes.
Trailer Brake DIC Display Page
The ITBC system displays
messages in the Driver Information
Center (DIC).
The display page indicates Trailer
Gain setting, power output to the
trailer brakes, trailer connection, and
system operational status.
To display the Trailer Brake Display
Page do any of the following:
.
Scroll through the DIC menu
pages.
.
Press a Trailer Gain button.
If the Trailer Brake Display Page
is not currently displayed, press

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - crc - 6/21/17
Driving and Operating 271a Trailer Gain button to recall the
current Trailer Gain setting.
Each press and release of the
gain buttons will then change the
Trailer Gain setting.
.
Activate the Manual Trailer
Brake apply lever.
TRAILER GAIN: This setting can be
adjusted from 0.0 to 10.0 with either
a trailer connected or disconnected.
To adjust the Trailer Gain, press one
of the Trailer Gain adjustment
buttons. Press and hold a gain
button to continuously adjust the
Trailer Gain. To turn the output to
the trailer off, adjust the Trailer Gain
setting to 0.0 (zero).
TRAILER OUTPUT: Displays any
time a trailer with electric brakes is
connected. Output to the trailer
brakes is based on the amount of
vehicle braking present and relative
to the Trailer Gain setting. Output is
displayed from 0 to 100% for each
gain setting. The Trailer Output will indicate “ - - -
- - - ” on the Trailer Brake Display
Page whenever the following occur:
.
No trailer is connected.
.
A trailer without electric brakes
is connected (no DIC message
displayed).
.
A trailer with electric brakes has
become disconnected (a
CHECK TRAILER WIRING
message will also display on
the DIC).
.
There is a fault present in the
wiring to the trailer brakes (a
CHECK TRAILER WIRING
message will also display on
the DIC).
.
The ITBC system is not working
due to a fault (a SERVICE
TRAILER BRAKE SYSTEM
message will also display in
the DIC).
Manual Trailer Brake Apply
The Manual Trailer Brake Apply
lever is used to apply the trailer ’ s
electric brakes independent of the
vehicle ’ s brakes. Sliding the lever to the left will apply only the trailer
brakes. Use this lever to adjust
Trailer Gain to properly adjust the
power output to the trailer brakes.
The trailer's and the vehicle's brake
lamps will come on when either
vehicle brakes or manual trailer
brakes are applied.
Trailer Gain Adjustment Procedure
Trailer Gain should be set for a
specific trailering condition and must
be adjusted any time vehicle
loading, trailer loading, or road
surface conditions change.
{ WarningTrailer brakes that are
over-gained or under-gained may
not stop the vehicle and the trailer
as intended and can result in a
crash. Always follow the
instructions to set the Trailer Gain
for the proper trailer stopping
performance.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - crc - 6/21/17
272 Driving and Operating To adjust Trailer Gain for each
towing condition:
1. Drive the vehicle with the trailer
attached on a level road
surface representative of the
towing condition and free of
traffic at about 32 to 40 km/h
(20 to 25 mph) and fully apply
the Manual Trailer Brake apply
lever.
Adjusting Trailer Gain at
speeds lower than 32 to
40 km/h (20 to 25 mph) may
result in an incorrect gain
setting.
2. Adjust the Trailer Gain, using
the Trailer Gain adjustment
buttons, to just below the point
of trailer wheel lock-up,
indicated by trailer wheel
squeal or tire smoke when a
trailer wheel locks.
Trailer wheel lock-up may not
occur if towing a heavily loaded
trailer. In this case, adjust the
Trailer Gain to the highest
allowable setting for the towing
condition. 3. Readjust Trailer Gain any time
vehicle loading, trailer loading,
or road surface conditions
change or if trailer wheel
lock-up is noticed at any time
while towing.
Other ITBC-Related DIC Messages
In addition to displaying TRAILER
GAIN and OUTPUT through the
DIC, trailer connection and ITBC
system status are displayed on
the DIC.
TRAILER CONNECTED: This
message will briefly display when a
trailer with electric brakes is first
connected to the vehicle. This
message will automatically turn off
in about 10 seconds. This message
can be acknowledged before it
automatically turns off.
CHECK TRAILER WIRING: This
message will display if:
.
The ITBC system first
determines connection to a
trailer with electric brakes and
then the trailer harness becomes
disconnected from the vehicle. If the disconnect occurs while
the vehicle is stationary, this
message will automatically turn
off in about 30 seconds. This
message will also turn off if it is
acknowledged or if the trailer
harness is reconnected.
If the disconnect occurs while
the vehicle is moving, this
message will continue until the
ignition is turned off. This
message will also turn off if it is
acknowledged or if the trailer
harness is reconnected.
.
There is an electrical fault in the
wiring to the trailer brakes. This
message will continue as long
as there is an electrical fault in
the trailer wiring. This message
will also turn off if it is
acknowledged.
To determine if the electrical fault is
on the vehicle side or trailer side of
the trailer wiring harness
connection:
1. Disconnect the trailer wiring
harness from the vehicle.
2. Turn the ignition off.