wheel GMC SIERRA 2015 Workshop Manual

Black plate (25,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-25
Do not turn the engine off when the
vehicle is moving. This will cause a
loss of power assist in the brake
and steering systems and disable
the airbags.
If the vehicle must be shut off in an
emergency:
1. Brake using a firm and steadypressure. Do not pump the
brakes repeatedly. This may
deplete power assist, requiring
increased brake pedal force.
2. Shift the vehicle to N (Neutral). This can be done while the
vehicle is moving. After shifting
to N (Neutral), firmly apply the
brakes and steer the vehicle to a
safe location.
3. Come to a complete stop, shift to P (Park), and turn the ignition
to LOCK/OFF. On vehicles with
an automatic transmission, the
shift lever must be in P (Park) to
turn the ignition switch to the
LOCK/OFF position. 4. Set the parking brake. See
Parking Brake on page 9-47.
{Warning
Turning off the vehicle while
moving may cause loss of power
assist in the brake and steering
systems and disable the airbags.
While driving, only shut the
vehicle off in an emergency.
If the vehicle cannot be pulled over,
and must be shut off while driving,
turn the ignition to ACC/
ACCESSORY.
{Caution
Using a tool to force the key to
turn in the ignition could cause
damage to the switch or break the
key. Use the correct key, make
sure it is all the way in, and turn it
only with your hand. If the key
cannot be turned by hand, see
your dealer. 2 (ACC/ACCESSORY):
This
position lets things like the radio
and the windshield wipers operate
while the engine is off. It also
unlocks the steering wheel. Use this
position if the vehicle must be
pushed or towed.
3 (ON/RUN): This position can be
used to operate the electrical
accessories and to display some
instrument cluster warning and
indicator lights. This position can
also be used for service and
diagnostics, and to verify the proper
operation of the malfunction
indicator lamp as may be required
for emission inspection purposes.
The switch stays in this position
when the engine is running. The
transmission is also unlocked in this
position on automatic transmission
vehicles.
If the key is left in the ACC/
ACCESSORY or ON/RUN position
with the engine off, the battery could
be drained. The vehicle may not
start if the battery is allowed to drain
for an extended period of time.

Black plate (26,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
9-26 Driving and Operating
4 (START):This is the position that
starts the engine. When the engine
starts, release the key. The ignition
switch returns to ON/RUN for
driving.
A warning tone will sound when the
driver door is opened and the
ignition is in ACC/ACCESSORY or
LOCK/OFF, and the key is in the
ignition.
Starting the Engine
If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
{Caution
If you add electrical parts or
accessories, you could change
the way the engine operates. Any
resulting damage would not be
covered by the vehicle warranty.
See Add-On Electrical Equipment
on page 9-88.
{Caution
If the steering wheel is turned
until it reaches the end of its
travel, and is held in that position
while starting the vehicle, damage
may occur to the hydraulic power
steering system and there may be
loss of power steering assist.
Move the shift lever to P (Park) or
N (Neutral). To restart the engine
when the vehicle is already moving,
use N (Neutral) only.
{Caution
Do not try to shift to P (Park) if the
vehicle is moving. If you do, you
could damage the transmission.
Shift to P (Park) only when the
vehicle is stopped.
Starting Procedure
1. Turn the ignition key to START. When the engine starts, let go of
the key. The idle speed will go
down as the engine gets warm.
Do not race the engine
immediately after starting it.
Operate the engine and
transmission gently to allow the
oil to warm up and lubricate all
moving parts.
When the low fuel warning light
is on and the FUEL LEVEL LOW
message is displayed in the
Driver Information Center (DIC),
hold the ignition switch in the
START position to continue
engine cranking.
{Caution
Cranking the engine for long
periods of time, by returning the
ignition to the START position
immediately after cranking has
ended, can overheat and damage
(Continued)

Black plate (27,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-27
Caution (Continued)
the cranking motor, and drain the
battery. Wait at least 15 seconds
between each try, to let the
cranking motor cool down.
2. If the engine does not start after five to 10 seconds, especially in
very cold weather (below −18°
C or 0°F), it could be flooded
with too much gasoline. Try
pushing the accelerator pedal all
the way to the floor and holding
it there while holding the key in
START for up to 15 seconds.
Wait at least 15 seconds
between each try, to allow the
cranking motor to cool down.
When the engine starts, let go of
the key and accelerator. If the
vehicle starts briefly but then
stops again, do the same thing.
This clears the extra gasoline
from the engine. Do not race the
engine immediately after starting
it. Operate the engine and transmission gently until the oil
warms up and lubricates all
moving parts.
Fast Idle System
If equipped, this feature is available
only with cruise control. The manual
fast idle switch is operated using the
cruise control buttons on the left
side of the steering wheel.
This system can be used to
increase engine idle speed
whenever the following conditions
are met:
.The parking brake is set.
.The brake pedal is not pressed.
.The vehicle must not be moving
and the accelerator must not be
pressed.
To control the fast idle:
.To enable the Fast Idle System,
press and release the cruise
control on/off button and ensure
that the switch indicator light
is lit.
.Press and release the cruise
control SET- button. Engine
speed will be held at
approximately 1200 rpm.
One of the following actions will turn
off the fast idle:
.Pressing the brake.
.Selecting the cruise control
cancel button.
.Releasing the parking brake.
.Moving the transmission shift
lever out of P (Park) or
N (Neutral).
.Selecting the cruise control on/
off button when it was
previously on.
.Pressing the cruise control SET-
button a second time.
.Pressing the accelerator more
than one-quarter of the
way down.
.Turning the ignition switch to the
LOCK/OFF position.

Black plate (30,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
9-30 Driving and Operating
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. If the vehicle has a
four-wheel drive transfer case
with a N (Neutral) position, and
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, seeDriving Characteristics
and Towing Tips on page 9-68. 1. Hold the brake pedal down, then
set the parking brake.
See Parking Brake on
page 9-47.
2. Move the shift lever into the P (Park) position by pulling the
shift lever toward you and
moving it up as far as it will go.
3. Be sure the transfer case is in a drive gear —not in N (Neutral).
4. Turn the ignition key to LOCK/OFF.
5. Remove the key and take it with you. If you can leave the vehicle
with the ignition key in your
hand, the vehicle is in P (Park).
Leaving the Vehicle with the
Engine Running
{Warning
It can be dangerous to leave the
vehicle with the engine running.
The vehicle could move suddenly
(Continued)
Warning (Continued)
if the shift lever is not fully in
P (Park) with the parking brake
firmly set.
If you have four-wheel drive and
the transfer case is in N (Neutral),
the vehicle will be free to roll,
even if the shift lever is in
P (Park). So be sure the transfer
case is in a drive gear —not in
N (Neutral).
And, if you leave the vehicle with
the engine running, it could
overheat and even catch fire. You
or others could be injured. Do not
leave the vehicle with the engine
running unless you have to.
If you have to leave the vehicle with
the engine running, be sure the
vehicle is in P (Park) and the
parking brake is firmly set before
you leave it. After you move the shift
lever into P (Park), hold the regular
brake pedal down. Then, see if you

Black plate (33,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-33
Warning (Continued)
.There are holes or openings
in the vehicle body from
damage or aftermarket
modifications that are not
completely sealed.
If unusual fumes are detected or
if it is suspected that exhaust is
coming into the vehicle:
.Drive it only with the windows
completely down.
.Have the vehicle repaired
immediately.
Never park the vehicle with the
engine running in an enclosed
area such as a garage or a
building that has no fresh air
ventilation.
Running the Vehicle
While Parked
It is better not to park with the
engine running.
If the vehicle is left with the engine
running, follow the proper steps to
be sure the vehicle will not move.
See Shifting Into Park on page 9-30
and Engine Exhaust on page 9-32.
If parking on a hill and pulling a
trailer, see Driving Characteristics
and Towing Tips on page 9-68.
Automatic
Transmission
If equipped, there is an electronic
shift lever position indicator within
the instrument cluster. This display
comes on when the ignition key is
turned to the ON/RUN position.
There are several different positions
for the shift lever.
Heavy-Duty 6-Speed Automatic
Transmission Shown, Others
Similar
See “Range Selection Mode” under
Manual Mode on page 9-36.
P (Park): This position locks the
rear wheels. It is the best position to
use when starting the engine
because the vehicle cannot move
easily. When parked on a hill,

Black plate (34,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
9-34 Driving and Operating
especially when the vehicle has a
heavy load, you might notice an
increase in the effort to shift out of
P (Park). See“Torque Lock” under
Shifting Into Park on page 9-30.
{Warning
It is 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.
Do not leave the vehicle when the
engine is running. 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,
always set the parking brake and
move the shift lever to P (Park).
See Shifting Into Park on
page 9-30 andDriving
Characteristics and Towing Tips
on page 9-68.
{Warning
If you have four-wheel drive, the
vehicle will be free to roll —even
if the shift lever is in P (Park) —if
the transfer case is in N (Neutral).
So, be sure the transfer case is in
a drive gear, Two-Wheel Drive
High or Four-Wheel Drive High or
Four-Wheel Drive Low —not in
N (Neutral). See Shifting Into Park
on page 9-30.
R (Reverse): Use this gear to
back up.
{Caution
Shifting to R (Reverse) while the
vehicle is moving forward could
damage the transmission. The
repairs would not be covered by
the vehicle warranty. Shift to
R (Reverse) only after the vehicle
is stopped. To rock the vehicle back and forth to
get out of snow, ice, or sand without
damaging the transmission, see
If
the Vehicle Is Stuck on page 9-14.
N (Neutral): In this position, the
engine does not connect with the
wheels. To restart when you are
already moving, use N (Neutral)
only. Also, use N (Neutral) when the
vehicle is being towed.
{Warning
Shifting into a drive gear while the
engine is running at high speed is
dangerous. Unless your foot is
firmly on the brake pedal, the
vehicle could move very rapidly.
You could lose control and hit
people or objects. Do not shift
into a drive gear while the engine
is running at high speed.

Black plate (39,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-39
Low Traction Mode
If equipped, Low Traction Mode
assists in vehicle acceleration when
road conditions are slippery, such
as with ice or snow. While the
vehicle is at a stop, select M2 using
Range Selection Mode. This will
limit torque to the wheels and help
to prevent the tires from spinning.
Tow/Haul Mode
The vehicle has a Tow/Haul Mode.
The Tow/Haul Mode adjusts the
transmission shift pattern to reduceshift cycling, providing increased
performance, vehicle control, and
enhanced transmission and engine
cooling when driving down steep
hills or mountain grades, towing,
or hauling heavy loads.
The selector button is on the end of
the shift lever. Turn the Tow/Haul
Mode on and off by pressing the
button. When the Tow/Haul Mode is
enabled, a light on the instrument
cluster will come on.
See
Tow/Haul Mode Light on
page 5-22 andHill and Mountain
Roads on page 9-11.
Also see “Tow/Haul Mode” under
Towing Equipment on page 9-78.
Tow/Haul Mode Grade Braking
Tow/Haul Mode Grade Braking is
only enabled while the Tow/Haul
Mode is selected and the vehicle is
not in the Range Selection Mode.
See “Tow/Haul Mode” listed
previously and Manual Mode on
page 9-36. Tow/Haul Mode Grade
Braking assists in maintaining desired vehicle speeds when driving
on downhill grades by using the
engine and transmission to slow the
vehicle.
On vehicles with a gasoline engine,
to disable or enable Tow/Haul
Grade Braking within the current
ignition key cycle, press and hold
the Tow/Haul button for
five seconds. When the button is
released, the requested mode
change is made. A DIC message is
displayed. See
Transmission
Messages on page 5-39.
On vehicles with a diesel engine,
Tow/Haul Mode Grade Braking can
be enabled or disabled by pressing
the Tow/Haul Mode button. Use the
exhaust brake and Tow/Haul Mode
for maximum grade braking.
See Towing Equipment on
page 9-78.
For other forms of grade braking,
see Automatic Transmission on
page 9-33 andCruise Control on
page 9-52.

Black plate (40,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
9-40 Driving and Operating
Drive Systems
Four-Wheel Drive
If equipped, four-wheel drive
engages the front axle for extra
traction. Read the appropriate
section for transfer case operation
before using.
{Caution
Driving on clean, dry pavement in
four-wheel drive for an extended
period of time may cause
premature wear on the system.
The damage would not be
covered by the vehicle warranty.
Driving on clean, dry pavement in
four-wheel drive may:
.Cause a vibration to be felt in
the steering system.
.Cause tires to wear faster.
.Make the transfer case harder to
shift, and cause it to run noisier.
{Warning
Shifting the transfer case to
N (Neutral) can cause the vehicle
to roll even if the transmission is
in P (Park). You or someone else
could be seriously injured. Be
sure to set the parking brake
before placing the transfer case in
N (Neutral). See Parking Brake on
page 9-47.
{Caution
Extended high-speed operation in
4
nmay damage or shorten the
life of the drivetrain.
Engagement noise and bump when
shifting between 4
nand 4mor from
N (Neutral), with the engine running,
is normal. Shifting into 4
nwill turn Traction
Control and StabiliTrak®off. See
Traction Control/Electronic Stability
Control on page 9-49.
Electronic Transfer Case
Use the transfer case knob, next to
the steering wheel, to shift into and
out of four-wheel drive for extra
traction.
Indicator lights on the knob show
which setting the transfer case is in.
The N (Neutral) indicator is on the
face of the knob. The indicator lights
display briefly when the ignition is

Black plate (41,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-41
turned on, and one will stay on.
If the lights display momentarily
when the ignition is in ON/RUN, but
none stay on, the knob may have
been turned while the vehicle was
off. To see the indicator, turn the
knob to another position so that it
matches the actual transfer case
setting. If no lights display, take the
vehicle to your dealer for service.
An indicator light flashes while
shifting and until the shift is
complete.
If the transfer case cannot complete
a requested shift, it will return to the
last chosen setting. Turn the control
back to the previous setting to see
the indicator light.
{Caution
Shifting the transmission into gear
before the requested mode
indicator light has stopped
flashing could damage the
transfer case.The settings are:
N (Neutral):
Shift the transfer case
to N (Neutral) only when towing the
vehicle. See Recreational Vehicle
Towing on page 10-91 orTowing the
Vehicle on page 10-91.
2
m(Two-Wheel Drive High): Use
for driving on most streets and
highways. The front axle is not
engaged. This setting provides the
best fuel economy.
4
n(Four-Wheel Drive Low): This
setting engages the front axle and
delivers extra torque. Choose 4
nif
driving off-road in deep sand, deep
mud, or deep snow, and while
climbing or descending steep hills.
When engaged, keep vehicle speed
below 72 km/h (45 mph).
Shifting into 4
nwill turn Traction
Control and StabiliTrak off. See
Traction Control/Electronic Stability
Control on page 9-49. 4
m(Four-Wheel Drive High):
Use
when extra traction is needed. The
front axle engages and helps when
driving on snowy or icy roads, when
off-roading, or when plowing snow.
The vehicle can be shifted from 2
m
to 4mwhile the vehicle is moving.
Shifting Into 4
m
Turn the knob to 4mat any speed
up to 121 km/h (75 mph), except
from 4
n. The indicator light will flash
while shifting and will remain on the
selected setting.
Shifting Into 2
m
Turn the knob to 2mat any speed,
except when shifting from 4
n.

Black plate (43,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-43
8. Turn the engine off, and theignition to ACC/ACCESSORY.
9. Place the transmission shift lever in P (Park).
10. See Recreational Vehicle
Towing on page 10-91.
11. Turn the ignition to LOCK/OFF.
Shifting Out of N (Neutral)
To shift out of N (Neutral):
1. Set the parking brake and apply the brake pedal.
2. Turn the ignition to ON/RUN with the engine off.
3. Shift the transmission to N (Neutral).
4. Turn the transfer case knob to 2
m.
After the transfer case has
shifted out of N (Neutral), the
N (Neutral) light will go out.
5. Release the parking brake.
{Caution
Shifting the transmission into gear
before the requested mode
indicator light has stopped
flashing could damage the
transfer case.
6. Start the engine and shift the transmission to the desired gear.
Automatic Transfer Case
Use the transfer case knob next to
the steering wheel to shift into and
out of four-wheel drive.
Indicator lights display which setting
the transfer case is in. N (Neutral) is
indicated on the face of the knob.
The indicator lights will display
briefly when the ignition is turned on
and one will stay on. If the lights
display momentarily when the
ignition is in ON/RUN, but none stay
on, the knob may have been turned
while the vehicle was off. To see the
indicator, turn the knob to another
position so that it matches the
actual transfer case setting. If no
lights display, take the vehicle to
your dealer for service. An indicator
light flashes while shifting the
transfer case and remains
illuminated when the shift is
complete.
If the transfer case cannot make a
requested shift, it will return to the
last chosen setting. Turn the knob
back to the previous transfer case
setting to see the indicator.