2015 GMC SIERRA 1500 ECU

Black plate (29,1)GMC Sierra Owner Manual (GMNA Localizing-U.S/Canada/Mexico-
7299746) - 2015 - crc - 11/11/13
Driving and Operating 9-29
An internal thermostat in the
plug-end of the cord may exist,
which will prevent engine coolant
heater operation at temperatures
above−18°C (0°F).
If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
To Use the Engine Coolant
Heater
1. Turn off the engine.
2. Open the hood and unwrap the electrical cord. The cord is
secured to the driver side fender
with a clip, next to the engine
compartment fuse block.
Carefully remove the wire tie
that bundles the electrical plug.
Do not cut the electrical cord.
3. Plug the cord into a normal, grounded 110-volt AC outlet.
{Warning
Plugging the cord into an
ungrounded outlet could cause an
electrical shock. Also, the wrong
kind of extension cord could
overheat and cause a fire. You
could be seriously injured. Plug
the cord into a properly grounded
three-prong 110-volt AC outlet.
If the cord will not reach, use a
heavy-duty three-prong extension
cord rated for at least 15 amps.
4. Before starting the engine, be sure to unplug and store the
cord as it was before to keep it
away from moving engine parts.
If you do not, it could be
damaged.
The length of time the heater should
remain plugged in depends on
several factors. Ask a dealer in the
area where you will be parking the
vehicle for the best advice on this.
Shifting Into Park
{Warning
It can be dangerous to get out of
the vehicle if the shift lever is not
fully in P (Park) with the parking
brake firmly set. The vehicle can
roll. If you have left the engine
running, the vehicle can move
suddenly. You or others could be
injured. To be sure the vehicle will
not move, even when you are on
fairly level ground, use the steps
that follow. With four-wheel drive,
if the transfer case is in
N (Neutral), the vehicle will be
free to roll, even if the shift lever
is in P (Park). Be sure the transfer
case is in a drive gear. If towing a
trailer, see Driving Characteristics
and Towing Tips on page 9-69.

Black plate (70,1)GMC Sierra Owner Manual (GMNA Localizing-U.S/Canada/Mexico-
7299746) - 2015 - crc - 11/11/13
9-70 Driving and Operating
{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.
.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 on page 9-32. 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.
Before starting, check all trailer hitch
parts and attachments, safety
chains, electrical connectors, lamps,
tires, and mirrors. 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
{Caution
Making very sharp turns while
trailering could cause the trailer to
come in contact with the vehicle.
(Continued)

Black plate (90,1)GMC Sierra Owner Manual (GMNA Localizing-U.S/Canada/Mexico-
7299746) - 2015 - crc - 11/11/13
9-90 Driving and Operating
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.
Heavy-Duty Trailer Wiring Harness
PackageFor vehicles equipped with
heavy-duty trailering, the harness
connector is mounted in the bumper.
The seven-wire harness contains
the following trailer circuits:
.Green/Violet: Left Stop/Turn
Signal
.Yellow/Gray: Right Stop/Turn
Signal
.Gray/Brown: Taillamps/Parking
Lamps
.White: Ground
.White/Green: Back-up Lamps
.Red/Green: Battery Feed
.Dark Blue: Trailer Brake
If charging a remote (non-vehicle)
battery, press the Tow/Haul Mode
button, if equipped, at the end of the
shift lever. This will boost the
vehicle system voltage and properly
charge the battery. If the trailer is
too light for Tow/Haul Mode, or the
vehicle is not equipped with Tow/ Haul, turn on the headlamps as a
second way to boost the vehicle
system and charge the battery.
Camper/Fifth-Wheel Trailer Wiring
Package
The 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: Left Stop/Turn
Signal
.Yellow/Gray: Right Stop/Turn
Signal
.Gray/Brown: Taillamps/Parking
Lamps
.White: Ground
.White/Green: Back-up Lamps
.Red/Green: Battery Feed
.Dark Blue: Trailer Brake

Black plate (98,1)GMC Sierra Owner Manual (GMNA Localizing-U.S/Canada/Mexico-
7299746) - 2015 - crc - 11/11/13
9-98 Driving and Operating
The plow the vehicle can carry
depends on many things, such as:
.The options the vehicle came
with, and the weight of those
options.
.The weight and number of
passengers intended to be
carried.
.The weight of items added to the
vehicle, like a tool box or
truck cap.
.The total weight of any
additional cargo intended to be
carried.
Say, for example, you have a 318 kg
(700 lb) snow plow. The total weight
of all occupants and cargo inside
the cab should not exceed 135 kg
(300 lb). This means that you may
only be able to carry one passenger.
But, even this may be too much if
there is other equipment already
adding to the weight of the vehicle. Here are some guidelines for safely
carrying a snow plow on the vehicle:
.Make sure the weight on the
front and rear axles does not
exceed the axle rating for each.
.For the front axle, if more cargo
or passengers must be carried,
appropriate counter ballast must
be installed rear of the rear axle.
Counter ballast must be properly
secured so it will not move
during driving.
.Follow the snow plow
manufacturer's
recommendations regarding rear
ballast. Rear ballast may be
required to ensure a proper front
and rear weight distribution ratio,
even though the actual weight at
the front axle may be less than
the front axle rating.
.The snow plow manufacturer or
installer can assist you in
determining the amount of rear
ballast required, to help make
sure the snow plow/vehicle
combination does not exceedthe GVW rating, the front and
rear axle ratings, and the front
and rear weight distribution ratio.
.The total vehicle must not
exceed the GVW rating.
Front axle reserve capacity is the
difference between the Gross Axle
Weight Rating (GAWR) and the front
axle weight of the vehicle with full
fuel and passengers. Basically, it is
the amount of weight that can be
added to the front axle before
reaching the front GAWR.

Black plate (23,1)GMC Sierra Owner Manual (GMNA Localizing-U.S/Canada/Mexico-
7299746) - 2015 - crc - 11/11/13
Vehicle Care 10-23
1. Remove the coolant surge tankpressure cap when the cooling
system, including the coolant
surge tank pressure cap and
upper radiator hose, is no
longer hot.
Turn the pressure cap slowly
counterclockwise about one full
turn. If a hiss is heard, wait for
that to stop. A hiss means there
is still some pressure left.
2. Keep turning the pressure cap slowly, and remove it.
3. Fill the coolant surge tank with the proper mixture to the FULL
COLD mark.
4. With the coolant surge tank pressure cap off, start the
engine and let it run until the
engine coolant temperature
gauge indicates approximately
90°C (195°F).
By this time, the coolant level
inside the coolant surge tank
may be lower. If the level is
lower, add more of the proper mixture to the coolant surge tank
until the level reaches the FULL
COLD mark.
5. Replace the pressure cap tightly.
6. Verify coolant level after the engine is shut off and the
coolant is cold. If necessary,
repeat coolant fill procedure
Steps 1–6.
{Caution
If the pressure cap is not tightly
installed, coolant loss and
possible engine damage may
occur. Be sure the cap is properly
and tightly secured.
Engine Overheating
If the vehicle has the Duramax
diesel engine, see the Duramax
diesel supplement.
{Caution
Running the engine without
coolant may cause damage or a
fire. Vehicle damage would not be
covered by the vehicle warranty.
The vehicle has several indicators
to warn of engine overheating.
There is a coolant temperature
gauge in the vehicle's instrument
cluster. See Engine Coolant
Temperature Gauge on page 5-16.
In addition, there are ENGINE
OVERHEATED STOP ENGINE,
ENGINE OVERHEATED IDLE
ENGINE, and ENGINE POWER IS
REDUCED messages in the Driver
Information Center (DIC). See
Engine Cooling System Messages
on page 5-37 andEngine Power
Messages on page 5-38.

Black plate (75,1)GMC Sierra Owner Manual (GMNA Localizing-U.S/Canada/Mexico-
7299746) - 2015 - crc - 11/11/13
Vehicle Care 10-75
Warning (Continued)
by the tire chains could cause you
to lose control of the vehicle and
you or others may be injured in a
crash.
Use another type of traction
device only if its manufacturer
recommends it for use on the
vehicle and tire size combination
and road conditions. Follow that
manufacturer's instructions. To
help avoid damage to the vehicle,
drive slowly, readjust, or remove
the device if it is contacting the
vehicle, and do not spin the
vehicle's wheels.
If you do find traction devices that
will fit, install them on the rear
tires.
{Caution
If the vehicle does not have dual
wheels and has a tire size other
than P265/65R18, P275/55R20,
LT265/70R17, LT265/70R18,
LT265/60R20, P285/50R20, 285/
45R22, or P285/45R22, use tire
chains only where legal and only
when you must. Use chains that
are the proper size for the tires.
Install them on the tires of the
rear axle. Do not use chains on
the tires of the front axle. Tighten
them as tightly as possible with
the ends securely fastened. Drive
slowly and follow the chain
manufacturer's instructions. If you
can hear the chains contacting
the vehicle, stop and retighten
them. If the contact continues,
slow down until it stops. Driving
too fast or spinning the wheels
with chains on will damage the
vehicle.
If a Tire Goes Flat
It is unusual for a tire to blowout
while driving, especially if the tires
are maintained properly. If air goes
out of a tire, it is much more likely to
leak out slowly. But if there ever is a
blowout, here are a few tips about
what to expect and what to do:
If a front tire fails, the flat tire
creates a drag that pulls the vehicle
toward that side. Take your foot off
the accelerator pedal and grip the
steering wheel firmly. Steer to
maintain lane position, and then
gently brake to a stop, well off the
road, if possible.
A rear blowout, particularly on a
curve, acts much like a skid and
may require the same correction as
used in a skid. Stop pressing the
accelerator pedal and steer to
straighten the vehicle. It may be
very bumpy and noisy. Gently brake
to a stop, well off the road,
if possible.

Black plate (82,1)GMC Sierra Owner Manual (GMNA Localizing-U.S/Canada/Mexico-
7299746) - 2015 - crc - 11/11/13
10-82 Vehicle Care
Rear Position–1500 Models 5. If the flat tire is on the rear, for
1500 models position the jack
under the rear axle about 5 cm
(2 in) inboard of the shock
absorber bracket.
Rear Position –All Other Models For all other models, position the
jack under the rear axle between
the spring anchor and the shock
absorber bracket.
If a snow plow has been added
to the front of the vehicle, lower
the snow plow fully before
raising the vehicle.
Make sure that the jack head is
positioned so that the rear axle
is resting securely between the
grooves that are on the
jack head.
{Warning
Getting under a vehicle when it is
lifted on a jack is dangerous.
If the vehicle slips off the jack,
you could be badly injured or
killed. Never get under a vehicle
when it is supported only by
a jack.

Black plate (87,1)GMC Sierra Owner Manual (GMNA Localizing-U.S/Canada/Mexico-
7299746) - 2015 - crc - 11/11/13
Vehicle Care 10-87
7. Make sure the tire is storedsecurely. Push, pull, and then try
to turn the tire. If the tire moves,
use the wheel wrench to tighten
the cable.
8. Reinstall the spare tire lock, if the vehicle has one. To store the jack and jack tools:
1. Wing Nut Retaining Wheel
Blocks
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 10-77.