trailer GMC SIERRA 2015 Service Manual

Black plate (86,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
9-86 Driving and Operating
3. Readjust Trailer Gain anytimevehicle 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 inthe 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

Black plate (87,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-87
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
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.
If 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. SeeTraction Control/
Electronic Stability Control on
page 9-49.
{Warning
Even 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 on page 9-78 for
trailer ratings and hitch setup
recommendations.
Adding non-dealer accessories can
affect the vehicle performance. See
Accessories and Modifications on
page 10-3.

Black plate (23,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Vehicle Care 10-23
If No Steam is Coming from
the Engine Compartment
The ENGINE OVERHEATED STOP
ENGINE or the ENGINE
OVERHEATED IDLE ENGINE
message, along with a low coolant
condition, can indicate a serious
problem.
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; seeTrailer Towing
on page 9-71.
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. Also, see
“Overheated
Engine Protection Operating Mode”
following.
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

Black plate (24,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
10-24 Vehicle Care
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
attempting any repair. Repair the
cause of coolant loss, change the
oil, and reset the oil life system.
SeeEngine Oil on page 10-8.
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
fans, 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 normaland 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)

Black plate (43,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Vehicle Care 10-43
Micro
J-Case Fuses Usage
1 Trailer Brake
2 Trailer Battery
J-Case Fuses Usage
3 Antilock Brake System Pump
4 Instrument Panel BEC 1
5 Spare
6 4WD Trec
7 Spare
8 Instrument Panel BEC 2
9 Spare
10 Rear Window Defogger
11 Starter J-Case
Fuses Usage
12 Cooling Fan 1
13 Cooling Fan 2
Mini Fuses (2 Pin) Usage
14 Trailer Stop/Turn Lamps, Left
15 Trailer Parking Lamps
16 Trailer Back-up Lamp
17 Trailer Stop/Turn Lamps, Right
Micro Fuses (2 Pin) Usage
18 Fuel Pump
19 Integrated Chassis Control Module Micro Fuses
(2 Pin) Usage
20 Electronic Suspension
Control Module
21 Fuel Pump Power Module
22 Upfitter Switch 1
23 Upfitter 2
24 Front Wiper
25 Antilock Brake System Valves
26 Upfitter SW 2
27 Upfitter SW 3
28 Parking Lamps, Right
29 Parking Lamps, Left
30 Upfitter 3
31 Upfitter SW 4
32 Upfitter 4

Black plate (45,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Vehicle Care 10-45
Micro
Relays Usage
64 Trailer Parking Lamps
65 Run/Crank
66 Upfitter 1
67 Fuel Pump 2
68 Air Conditioning Control
69 Starter Mini Relays Usage
70 Rear Window Defogger
71 Engine Control Module
Solid State Relay Usage
72 Cooling Fan ClutchInstrument Panel Fuse
Block (Left)
The left instrument panel fuse block
access door is on the driver side
edge of the instrument panel.
Pull off the cover to access the fuse
block.

Black plate (53,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Vehicle Care 10-53
DOT Tire Date of
Manufacture
:The last four
digits of the TIN indicate the tire
manufactured date. The first two
digits represent the week
(01-52) and the last two digits,
the year. For example, the third
week of the year 2010 would
have a four-digit DOT date
of 0310.
(4) Tire Identification Number
(TIN)
:The letters and numbers
following the DOT code are the
Tire Identification Number (TIN).
The TIN shows the
manufacturer and plant code,
tire size, and date the tire was
manufactured. The TIN is
molded onto both sides of the
tire, although only one side may
have the date of manufacture.
(5) Tire Ply Material
:The type
of cord and number of plies in
the sidewall and under the tread. (6) Uniform Tire Quality
Grading (UTQG)
:Tire
manufacturers are required to
grade tires based on three
performance factors: treadwear,
traction, and temperature
resistance. For more
information, see Uniform Tire
Quality Grading on page 10-71.
(7) Maximum Cold Inflation
Load Limit
:Maximum load that
can be carried and the
maximum pressure needed to
support that load. For
information on recommended
tire pressure see Tire Pressure
on page 10-59 andVehicle Load
Limits on page 9-15.
(8) Temporary Use Only
:Only
use a temporary spare tire until
the road tire is repaired and
replaced. This spare tire should
not be driven on over 112 km/h
(70 mph), or 88 km/h (55 mph)
when pulling a trailer, with the proper inflation pressure. See
Full-Size Spare Tire on
page 10-86.
Light Truck (LT-Metric) Tire
(1) Tire Size:The tire size code
is a combination of letters and
numbers used to define a
particular tire's width, height,
aspect ratio, construction type,
and service description. See the
“Tire Size” illustration later in this
section for more detail.

Black plate (86,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
10-86 Vehicle Care
To store the jack and jack tools:
1. Wing Nut Retaining WheelBlocks
2. Wheel Blocks
3. Wing Nut Retaining Tool Kit
4. Wheel Wrench and Extensions
5. Tool Bag
6. Jack Mounting Bracket
7. Jack
8. Bolt Retaining Wheel Blocks
1. Put the tools (4) in the tool bag (5) and place them in the
retaining bracket (3). 2. Tighten down the wing nut (3).
3. Assemble the wheel blocks (2)
and jack (7) together with the
wing nut (1) and retaining
bolt (8).
4. Position the jack (7) in the mounting bracket (6). Position
the holes in the base of the
jack (7) onto the pin in the
mounting bracket (6).
5. Return them to their original location in the vehicle. See
“Removing the Spare Tire and
Tools.”
Full-Size Spare Tire
If this vehicle came with a full-size
spare tire, it was fully inflated when
new, however, it can lose air over
time. Check the inflation pressure
regularly. See Tire Pressure on
page 10-59 andVehicle Load Limits
on page 9-15. For instructions on
how to remove, install, or store a
spare tire, see Tire Changing on
page 10-76. If equipped with a temporary use
full-size spare tire, it is indicated on
the tire sidewall. See
Tire Sidewall
Labeling on page 10-52. This spare
tire should not be driven on over
112 km/h (70 mph), or 88 km/h
(55 mph) when pulling a trailer, at
the proper inflation pressure.
Repair and replace the road tire as
soon as it is convenient, and stow
the spare tire for future use.
{Caution
If the vehicle has four-wheel drive
and a different size spare tire is
installed, do not drive in
four-wheel drive until the flat tire
is repaired and/or replaced. The
vehicle could be damaged and
the repairs would not be covered
by the warranty. Never use
four-wheel drive when a different
size spare tire is installed on the
vehicle.

Black plate (92,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
10-92 Vehicle Care
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.
{Caution
Use 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
{Caution
If 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 VehiclesOnly 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.

Black plate (2,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
11-2 Service and Maintenance
The Tire Rotation and Required
Services are the responsibility of the
vehicle owner. It is recommended to
have your dealer perform these
services every 12 000 km/7,500 mi.
Proper vehicle maintenance helps to
keep the vehicle in good working
condition, improves fuel economy,
and reduces vehicle emissions.
Because of the way people use
vehicles, maintenance needs vary.
There may need to be more
frequent checks and services.
Normal Service
All maintenance services, including
those listed under Additional
Required Services, are for
vehicles that:
.Carry passengers and cargo
within recommended limits on
the Tire and Loading Information
label. SeeVehicle Load Limits
on page 9-15.
.Are driven on reasonable road
surfaces within legal driving
limits.
.Use the recommended fuel. See
Fuel on page 9-63.
Severe Service
In addition to the normal service
schedule, some vehicles require
service more often. Severe service
is for vehicles that are:
.Mainly driven in heavy city traffic
in hot weather.
.Mainly driven in hilly or
mountainous terrain.
.Frequently towing a trailer.
.Used for high-speed or
competitive driving.
.Used for taxi, police, or delivery
service.
{Warning
Performing maintenance work can
be dangerous and can cause
serious injury. Perform
maintenance work only if the
required information, proper tools,
and equipment are available.
If they are not, see your dealer to
have a trained technician do the
work. See Doing Your Own
Service Work on page 10-3.