
GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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326 Driving and Operating
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 being
towed weighs up to 2 271 kg
(5,000 lb) 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.
Be sure to 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.
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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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Driving and Operating 327
Use only a round, seven-wire
connector with flat blade terminals
meeting SAE J2863 specifications
for proper electrical connectivity.
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.
Heavy-Duty Trailer Wiring Harness
Package
For vehicles equipped with
heavy-duty trailering, the harness
connector is mounted in the bumper.
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: 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.
Camper/Fifth-Wheel Trailer Wiring
Package
For vehicles without the fifth wheel/
gooseneck tralier 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

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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Driving and Operating 329
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 brakesystem, 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
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/RUN.
{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
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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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Driving and Operating 331
.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 anytime vehicle loading,
trailer loading, or road surface
conditions change.
{Warning
Trailer 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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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Driving and Operating 333
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.
If TSC is enabled, the Traction
Control System (TCS)/StabiliTrak
warning light will flash on theinstrument 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 0284.
{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 0324 for trailer ratings
and hitch setup
recommendations. Adding non-dealer accessories can
affect the vehicle performance. See
Accessories and
Modifications
0341.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
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336 Driving and Operating
amount of weight that can be added
to the front axle before reaching the
front GAWR.
United States
Canada
The front axle reserve capacity for
the vehicle is in the lower right
corner of the Certification/Tire label.
To calculate the amount of weight
any front accessory, such as a snow
plow, is adding to the front axle, use
this formula:(W x (A + W.B.)) /W.B.= Weight the
accessory is adding to the
front axle.
Where: W = Weight of added accessory
A = Distance that the accessory
is in front of the front axle
W.B. = Vehicle Wheelbase
For example, adding a 318 kg
(700 lb) snow plow actually adds
more than 318 kg (700 lb) to the
front axle. Using the formula, if the
snow plow is 122 cm (4 ft) in front of
the front axle and the wheelbase is
305 cm (10 ft), then: W = 318 kg (700 lb)
A = 122 cm (4 ft)

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Vehicle Care 339
Vehicle Care
General Information
General Information . . . . . . . . . . 340
California Proposition65 Warning . . . . . . . . . . . . . . . . . 340
California Perchlorate Materials Requirements . . . . . 341
Accessories and Modifications . . . . . . . . . . . . . . . . 341
Vehicle Checks
Doing Your OwnService Work . . . . . . . . . . . . . . . 342
Hood . . . . . . . . . . . . . . . . . . . . . . . . . 342
Engine Compartment Overview . . . . . . . . . . . . . . . . . . . . 343
Engine Oil . . . . . . . . . . . . . . . . . . . . 348
Engine Oil Life System . . . . . . . 351
Automatic Transmission Fluid (6 Speed Transmission) . . . . . 352
Automatic Transmission Fluid (8 Speed Transmission) . . . . . 354
Engine Air Cleaner/Filter . . . . . . 355
Cooling System . . . . . . . . . . . . . . 356
Engine Coolant . . . . . . . . . . . . . . . 357
Engine Overheating . . . . . . . . . . 360
Overheated Engine Protection Operating Mode . . . . . . . . . . . . . 362
Engine Fan . . . . . . . . . . . . . . . . . . . 362 Power Steering Fluid (1500
Series) . . . . . . . . . . . . . . . . . . . . . . 363
Power Steering Fluid (2500/ 3500 Series) . . . . . . . . . . . . . . . . 363
Washer Fluid . . . . . . . . . . . . . . . . . 363
Brakes . . . . . . . . . . . . . . . . . . . . . . . 364
Brake Fluid . . . . . . . . . . . . . . . . . . . 365
Battery - North America . . . . . . 366
Four-Wheel Drive . . . . . . . . . . . . . 367
Front Axle . . . . . . . . . . . . . . . . . . . . 368
Rear Axle . . . . . . . . . . . . . . . . . . . . 368
Noise Control System . . . . . . . . 370
Starter Switch Check . . . . . . . . . 371
Automatic Transmission Shift
Lock Control Function
Check . . . . . . . . . . . . . . . . . . . . . . . 371
Ignition Transmission Lock Check . . . . . . . . . . . . . . . . . . . . . . . 371
Park Brake and P (Park) Mechanism Check . . . . . . . . . . 371
Wiper Blade Replacement . . . . 372
Glass Replacement . . . . . . . . . . 372
Headlamp Aiming
Headlamp Aiming . . . . . . . . . . . . 373
Bulb Replacement
Bulb Replacement . . . . . . . . . . . . 373
Halogen Bulbs . . . . . . . . . . . . . . . . 373
High Intensity Discharge (HID) Lighting . . . . . . . . . . . . . . . . . . . . . 373 LED Lighting . . . . . . . . . . . . . . . . . 373
Taillamps, Turn Signal,
Stoplamps, and Back-Up
Lamps . . . . . . . . . . . . . . . . . . . . . . 374
Center High-Mounted
Stoplamp (CHMSL) and
Cargo Lamp . . . . . . . . . . . . . . . . . 375
Replacement Bulbs . . . . . . . . . . . 375
Electrical System
High Voltage Devices and Wiring . . . . . . . . . . . . . . . . . . . . . . . 376
Electrical System Overload . . . 376
Fuses . . . . . . . . . . . . . . . . . . . . . . . . 376
Engine Compartment Fuse Block . . . . . . . . . . . . . . . . . . . . . . . . 376
Instrument Panel Fuse Block
(Right) . . . . . . . . . . . . . . . . . . . . . . 379
Instrument Panel Fuse Block (Left) . . . . . . . . . . . . . . . . . 381
Wheels and Tires
Tires . . . . . . . . . . . . . . . . . . . . . . . . . . 383
All-Season Tires . . . . . . . . . . . . . . 384
Winter Tires . . . . . . . . . . . . . . . . . . 384
Low-Profile Tires . . . . . . . . . . . . . 385
All-Terrain Tires . . . . . . . . . . . . . . . 385
Tire Sidewall Labeling . . . . . . . . 385
Tire Designations . . . . . . . . . . . . . 388
Tire Terminology andDefinitions . . . . . . . . . . . . . . . . . . 389

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340 Vehicle Care
Tire Pressure . . . . . . . . . . . . . . . . . 391
Tire Pressure for High-SpeedOperation . . . . . . . . . . . . . . . . . . . 393
Tire Pressure Monitor System . . . . . . . . . . . . . . . . . . . . . . 393
Tire Pressure Monitor Operation . . . . . . . . . . . . . . . . . . . 394
Tire Inspection . . . . . . . . . . . . . . . . 397
Tire Rotation . . . . . . . . . . . . . . . . . 398
When It Is Time for New Tires . . . . . . . . . . . . . . . . . . . . . . . . 400
Buying New Tires . . . . . . . . . . . . . 401
Different Size Tires and Wheels . . . . . . . . . . . . . . . . . . . . . . 402
Uniform Tire Quality Grading . . . . . . . . . . . . . . . . . . . . . 403
Wheel Alignment and Tire Balance . . . . . . . . . . . . . . . . . . . . . 404
Wheel Replacement . . . . . . . . . . 404
Tire Chains . . . . . . . . . . . . . . . . . . . 405
If a Tire Goes Flat . . . . . . . . . . . . 406
Tire Changing . . . . . . . . . . . . . . . . 408
Full-Size Spare Tire . . . . . . . . . . 417
Jump Starting
Jump Starting - North America . . . . . . . . . . . . . . . . . . . . . 418
Towing the Vehicle
Towing the Vehicle . . . . . . . . . . . 422 Recreational Vehicle
Towing . . . . . . . . . . . . . . . . . . . . . . 423
Appearance Care
Exterior Care . . . . . . . . . . . . . . . . . 427
Interior Care . . . . . . . . . . . . . . . . . . 432
Floor Mats . . . . . . . . . . . . . . . . . . . . 435
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:
California Proposition
65 Warning
WARNING: Most motor vehicles,
including this one, as well as many
of its service parts and fluids,
contain and/or emit chemicals
known to the State of California to