towing GMC SIERRA DENALI 2018 Service Manual

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 333The 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 anytime 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.
Use the following 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 anytime
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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
334 Driving and Operating 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.
3. Wait 10 seconds, then turn the
ignition back to RUN.
4. If the CHECK TRAILER
WIRING message reappears,
the electrical fault is on the
vehicle side. If the CHECK TRAILER
WIRING message only
reappears when connecting the
trailer wiring harness to the
vehicle, the electrical fault is on
the trailer side.
SERVICE TRAILER BRAKE
SYSTEM: This message will display
when there is a problem with the
ITBC system. If this message
continues over multiple ignition
cycles, there is a problem with the
ITBC system. Have the vehicle
serviced.
If either the CHECK TRAILER
WIRING or SERVICE TRAILER
BRAKE SYSTEM message displays
while driving, the ITBC system may
not be fully functional or may not
function at all. When traffic
conditions allow, carefully pull the
vehicle over to the side of the road
and turn the ignition off. Check the
wiring connection to the trailer and
turn the ignition back on. If either of
these messages continues, either
the vehicle or trailer needs service. A GM dealer may be able to
diagnose and repair problems with
the trailer. However, any diagnosis
and repair of the trailer is not
covered under the vehicle warranty.
Contact your trailer dealer for
assistance with trailer repairs and
trailer warranty information.
Trailer Sway
Control (TSC) Vehicles with StabiliTrak have a
Trailer Sway Control (TSC) feature.
Trailer sway is unintended
side-to-side motion of a trailer while
being towed. If the vehicle is towing
a trailer and the TSC detects that
sway is increasing, the vehicle
brakes are selectively applied at
each wheel, to help reduce
excessive trailer sway. If the vehicle
is equipped with the Integrated
Trailer Brake Control (ITBC) system,
and the trailer has the electric
actuated brake system, StabiliTrak
may also apply the trailer brakes.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 335If TSC is enabled, the Traction
Control System (TCS)/StabiliTrak
warning light will flash on the
instrument cluster. Vehicle speed
must be reduced. If trailer sway
continues, StabiliTrak can reduce
engine torque to help slow the
vehicle. See Traction Control/
Electronic Stability Control 0 282 .
{ WarningEven if the vehicle is equipped
with TSC, trailer sway could result
in loss of control and the vehicle
could crash. If excessive trailer
sway is detected, slow down to a
safe speed. Check the trailer and
vehicle to help correct possible
causes. These could include an
improperly or overloaded trailer,
unrestrained cargo, improper
trailer hitch configuration,
excessive vehicle-trailer speed,
or improperly inflated or incorrect
vehicle or trailer tires. See Towing
Equipment 0 325 for trailer
ratings and hitch setup
recommendations. Adding non-dealer accessories can
affect the vehicle performance. See
Accessories and Modifications
0 343 .
Electronic Trailer Sway Control
Devices Some trailers may come equipped
with an electronic device designed
to reduce or control trailer sway.
Aftermarket equipment
manufacturers also offer similar
devices that connect to the wiring
between the trailer and the vehicle.
These devices may interfere with
the vehicle ’ s trailer brake or other
systems, including integrated
anti-sway systems, if equipped.
Messages related to trailer
connections or trailer brakes could
appear on the Driver Information
Center (DIC). The effect that these
devices may have on vehicle
handling or trailer brake
performance is unknown. { WarningUse of electronic trailer sway
control devices could result in
reduced trailer brake
performance, loss of trailer
brakes, or other malfunctions, and
could cause a crash. You or
others could be injured or killed.
Before using one of these
devices:
.
Ask the device or trailer
manufacturer if the device
has been thoroughly tested
for compatibility with the
make, model, and year of
the vehicle as well as
optional equipment installed
on the vehicle.
.
Before driving on the open
roads, check that the trailer
brakes are working properly.
Drive the vehicle with the
trailer attached on a level
road surface that is free of
traffic at about 32-40 km/h
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
342 Vehicle Care Tire Terminology and
Definitions . . . . . . . . . . . . . . . . . . 395
Tire Pressure . . . . . . . . . . . . . . . . . 397
Tire Pressure for High-Speed
Operation . . . . . . . . . . . . . . . . . . . 399
Tire Pressure Monitor
System . . . . . . . . . . . . . . . . . . . . . . 399
Tire Pressure Monitor
Operation . . . . . . . . . . . . . . . . . . . 400
Tire Inspection . . . . . . . . . . . . . . . . 404
Tire Rotation . . . . . . . . . . . . . . . . . 405
When It Is Time for New
Tires . . . . . . . . . . . . . . . . . . . . . . . . 407
Buying New Tires . . . . . . . . . . . . . 408
Different Size Tires and
Wheels . . . . . . . . . . . . . . . . . . . . . . 409
Uniform Tire Quality
Grading . . . . . . . . . . . . . . . . . . . . . 410
Wheel Alignment and Tire
Balance . . . . . . . . . . . . . . . . . . . . . 411
Wheel Replacement . . . . . . . . . . 412
Tire Chains . . . . . . . . . . . . . . . . . . . 413
If a Tire Goes Flat . . . . . . . . . . . . 413
Tire Changing . . . . . . . . . . . . . . . . 415
Full-Size Spare Tire . . . . . . . . . . 425
Jump Starting
Jump Starting - North
America . . . . . . . . . . . . . . . . . . . . . 426 Towing the Vehicle Towing the Vehicle . . . . . . . . . . . 430
Recreational Vehicle
Towing . . . . . . . . . . . . . . . . . . . . . . 430
Appearance Care Exterior Care . . . . . . . . . . . . . . . . . 435
Interior Care . . . . . . . . . . . . . . . . . . 441
Floor Mats . . . . . . . . . . . . . . . . . . . . 444
General Information For service and parts needs, visit
your dealer. You will receive
genuine GM parts and GM-trained
and supported service people.
Genuine GM parts have one of
these marks:

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
364 Vehicle Care If there is an engine overheat
warning, but no steam is seen or
heard, the problem may not be too
serious. Sometimes the engine can
get a little too hot when the vehicle:
.
Climbs a long hill on a hot day.
.
Stops after high-speed driving.
.
Idles for long periods in traffic.
.
Tows a trailer; see Trailer Towing
0 307 .
If the ENGINE OVERHEATED
STOP ENGINE or the ENGINE
OVERHEATED IDLE ENGINE
message appears with no sign of
steam, try this for a minute or so:
1. Turn the air conditioning off.
2. Turn the heater on to the
highest temperature and to the
highest fan speed. Open the
windows as necessary.
3. When it is safe to do so, pull off
the road, shift to P (Park) or
N (Neutral) and let the
engine idle. If the temperature overheat gauge is
no longer in the overheat zone or an
overheat warning no longer
displays, the vehicle can be driven.
Continue to drive the vehicle slowly
for about 10 minutes. Keep a safe
vehicle distance from the vehicle in
front. If the warning does not come
back on, continue to drive normally
and have the cooling system
checked for proper fill and function.
If the warning continues, pull over,
stop, and park the vehicle
right away.
If there is still no sign of steam and
the vehicle is equipped with an
engine driven cooling fan, push
down the accelerator until the
engine speed is about twice as fast
as normal idle speed for at least
five minutes while the vehicle is
parked. If the warning is still there,
turn off the engine and get everyone
out of the vehicle until it cools down.
If there is no sign of steam, idle the
engine for five minutes while
parked. If the warning is still
displayed, turn off the engine until it
cools down. Overheated Engine
Protection
Operating Mode If an overheated engine condition
exists and the ENGINE POWER IS
REDUCED message displays, an
overheat protection mode which
alternates firing groups of cylinders
helps to prevent engine damage. In
this mode, a loss in power and
engine performance will be noticed.
This operating mode allows the
vehicle to be driven to a safe place
in an emergency. Driving extended
distances and/or towing a trailer in
the overheat protection mode
should be avoided.
Caution
After driving in the overheated
engine protection operating
mode, the engine oil will be
severely degraded. Any repairs
performed before the engine is
cool may cause engine damage.
Allow the engine to cool before
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Vehicle Care 365Caution (Continued)attempting any repair. Repair the
cause of coolant loss, change the
oil, and reset the oil life system.
See Engine Oil 0 350 .
Engine Fan If the vehicle has a clutched engine
cooling fan, when the clutch is
engaged, the fan spins faster to
provide more air to cool the engine.
In most everyday driving conditions,
the fan is spinning slower and the
clutch is not fully engaged. This
improves fuel economy and reduces
fan noise. Under heavy vehicle
loading, trailer towing, and/or high
outside temperatures, the fan speed
increases as the clutch more fully
engages, so an increase in fan
noise may be heard. This is normal
and should not be mistaken as the
transmission slipping or making
extra shifts. It is merely the cooling
system functioning properly. The fan will slow down when additional
cooling is not required and the
clutch disengages.
This fan noise may also be heard
when starting the engine. It will go
away as the fan clutch partially
disengages.
If the vehicle has electric cooling
fan(s), the fans may be heard
spinning at low speed during most
everyday driving. The fans may turn
off if no cooling is required. Under
heavy vehicle loading, trailer towing,
high outside temperatures,
or operation of the air conditioning
system, the fans may change to
high speed and an increase in fan
noise may be heard. This is normal
and indicates that the cooling
system is functioning properly. The
fans will change to low speed when
additional cooling is no longer
required.
The electric engine cooling fans
may run after the engine has been
turned. off. This is normal and no
service is required. Power Steering Fluid
(1500 Series) The vehicle has electric power
steering and does not use power
steering fluid.
Power Steering Fluid
(2500/3500 Series)
See Engine Compartment Overview
0 345 for reservoir location.
When to Check Power Steering
Fluid It is not necessary to regularly
check power steering fluid unless
there is a leak suspected in the
system or an unusual noise is
heard. A fluid loss in this system
could indicate a problem. Have the
system inspected and repaired.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
430 Vehicle Care CautionIf the jumper cables are
connected or removed in the
wrong order, electrical shorting
may occur and damage the
vehicle. The repairs would not be
covered by the vehicle warranty.
Always connect and remove the
jumper cables in the correct order,
making sure that the cables do
not touch each other or other
metal.
Jumper Cable Removal
Reverse the sequence exactly when
removing the jumper cables.
After starting the disabled vehicle
and removing the jumper cables,
allow it to idle for several minutes. Towing the Vehicle CautionIncorrectly towing a disabled
vehicle may cause damage. The
damage would not be covered by
the vehicle warranty.
Do not lash or hook to
suspension components. Use the
proper straps around the tires to
secure the vehicle.
Use only a flatbed tow truck for
towing a disabled vehicle. Never
use a sling type lift or damage will
occur. Use ramps to help reduce
approach angles if necessary.
A towed vehicle should have its
drive wheels off the ground.
Consult a professional towing
service if the disabled vehicle must
be towed. Front Attachment Points
The vehicle is equipped with
specific attachment points to be
used to pull the vehicle onto a
flatbed car carrier from a flat road
surface. Do not use these
attachment points to pull the vehicle
from snow, mud or sand.
Recreational Vehicle
Towing Recreational vehicle towing means
towing the vehicle behind another
vehicle, such as a motor home. The
two most common types of

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Vehicle Care 431recreational vehicle towing are
dinghy and dolly towing. Dinghy
towing is towing the vehicle with all
four wheels on the ground. Dolly
towing is towing the vehicle with two
wheels on the ground and two
wheels on a dolly.
Follow the tow vehicle
manufacturer ’ s instructions. See
your dealer or trailering professional
for additional advice and equipment
recommendations.
CautionUse of a shield mounted in front
of the vehicle grille could restrict
airflow and cause damage to the
transmission. The repairs would
not be covered by the vehicle
warranty. If using a shield, only
use one that attaches to the
towing vehicle. Dinghy Towing Two-Wheel-Drive Vehicles
CautionIf the two-wheel-drive vehicle is
towed with all four wheels on the
ground, the drivetrain
components could be damaged.
The repairs would not be covered
by the vehicle warranty.
Two-wheel-drive vehicles should not
be towed with all four wheels on the
ground. Four-Wheel-Drive Vehicles
Only dinghy tow four-wheel-drive
vehicles with a two-speed transfer
case that have an N (Neutral) and a
Four-Wheel Drive Low (4 (
n ) setting.
{ Warning
Shifting a four-wheel-drive
vehicle's transfer case into
N (Neutral) can cause the vehicle
to roll even if the transmission is
in P (Park). You or others could
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Vehicle Care 4336. 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
Caution
If a two-wheel-drive vehicle is
towed with the rear wheels on the
ground, the transmission could be
damaged. The repairs would not
be covered by the vehicle
warranty. Never tow the vehicle
with the rear wheels on the
ground. Two-wheel-drive vehicles should not
be towed with the rear wheels on
the ground. Two-wheel-drive
transmissions have no provisions
for internal lubrication while being
towed.
To dolly tow a two-wheel-drive
vehicle, the vehicle must be towed
with the rear wheels on the dolly.
See “ Rear Towing (Rear Wheels Off
the Ground) ” later in this section.
Front Towing (Front Wheels Off
the Ground) – Four-Wheel-Drive
Vehicles

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
434 Vehicle Care To dolly tow a four-wheel-drive
vehicle from the front:
1. Attach the dolly to the tow
vehicle following the dolly
manufacturer's instructions.
2. Drive the front wheels onto the
dolly.
3. Shift the transmission to
P (Park).
4. Set the parking brake.
{ WarningShifting a four-wheel-drive
vehicle's transfer case into
N (Neutral) can cause the vehicle
to roll even if the transmission is
in P (Park). You or others could
be injured. Set the parking brake
before shifting the transfer case
to N (Neutral). 5. Use a clamping device
designed for towing to ensure
that the front wheels are locked
into the straight position.
6. Secure the vehicle to the dolly
following the manufacturer's
instructions.
7. Shift the transfer case to
N (Neutral). See “ Shifting into
N (Neutral) ” under Four-Wheel
Drive 0 272 for the proper
procedure.
8. Release the parking brake only
after the vehicle being towed is
firmly attached to the tow
vehicle.
9. Turn the ignition off. Rear Towing (Rear Wheels Off
the Ground) Two-Wheel-Drive Vehicles
To dolly tow a two-wheel-drive
vehicle from the rear:
1. Drive the rear wheels onto the
dolly.
2. Set the parking brake. See
Parking Brake 0 281 .
3. Put the transmission in
P (Park).
4. Secure the vehicle to the dolly
following the manufacturer's
instructions.