
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 9-25Do 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 steady
pressure. 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 .
{ WarningTurning 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 (27,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-27Caution (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 (29,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-29Warning (Continued) vehicle. Possible heater cord
and thermostat damage could
occur. .
While in use, do not let the
heater cord touch vehicle
parts or sharp edges. Never
close the hood on the
heater cord. .
Before starting the vehicle,
unplug the cord, reattach the
cover to the plug, and
securely fasten the cord.
Keep the cord away from any
moving parts.
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.
Retained Accessory
Power (RAP) The following vehicle accessories
can be used for up to 10 minutes
after the engine is turned off: .
Audio System .
Power Windows .
OnStar System (if equipped) .
Sunroof (if equipped)
These features work when the key
is in ON/RUN or ACC/
ACCESSORY. Once the key is
turned from ON/RUN to LOCK/OFF,
the windows and sunroof continue
to work up to 10 minutes or until any
door is opened. The radio continues
to work for up to 10 minutes or until
the driver door is opened. Accessory Power Outlets (APOs)
The vehicle may have APOs in
several locations. See Power
Outlets on page 5-5 .
The APOs in the console or center
seat position are powered by RAP.
They will continue to work for up to
10 minutes after the key is turned
from ON/RUN to LOCK/OFF, or until
the driver door is opened.
The APOs on the center stack come
from the factory powered directly
from the vehicle battery, and supply
accessory power at all times,
regardless of ignition key position.
If electronic items are left plugged
into these APOs for long periods of
time with the vehicle off, the vehicle
battery could be drained. The
vehicle may not start if the battery is
allowed to drain for an extended
period of time.

Black plate (31,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-31can move the shift lever away from
P (Park) without first pulling it toward
you. If you can, it means that the
shift lever was not fully locked into
P (Park).
Torque Lock If you are parking on a hill and you
do not shift the transmission into
P (Park) properly, the weight of the
vehicle may put too much force on
the parking pawl in the
transmission. You may find it difficult
to pull the shift lever out of P (Park).
This is called torque lock. To
prevent torque lock, set the parking
brake and then shift into P (Park)
properly before you leave the driver
seat. To find out how, see Shifting
Into Park on page 9-30 .
When you are ready to drive, move
the shift lever out of P (Park) before
you release the parking brake.
If torque lock does occur, you may
need to have another vehicle push
yours a little uphill to take some of
the pressure from the parking pawl in the transmission. You will then be
able to pull the shift lever out of
P (Park).
Shifting out of Park This vehicle is equipped with an
electronic shift lock release system.
The shift lock release is
designed to: .
Prevent ignition key removal
unless the shift lever is in
P (Park). .
Prevent movement of the shift
lever out of P (Park), unless the
ignition is in ON/RUN and the
regular brake pedal is applied.
The shift lock release is always
functional except in the case of an
uncharged or low voltage (less than
9 volt) battery.
If the vehicle has an uncharged
battery or a battery with low voltage,
try charging or jump starting the
battery. See Jump Starting on
page 10-87 . To shift out of P (Park):
1. Apply the brake pedal.
2. Move the shift lever to the
desired position.
If you still are unable to shift out of
P (Park):
1. Ease the pressure on the shift
lever.
2. While holding down the brake
pedal, press the shift lever all
the way into P (Park).
3. Move the shift lever to the
desired position.
If you are still having a problem
shifting, then have the vehicle
serviced soon.
This vehicle may have the Safety
Belt Assurance System, which may
prevent the vehicle from shifting out
of P (Park). See Safety Belt
Messages on page 5-37 .

Black plate (93,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Vehicle Care 10-93
{ 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).
Follow these steps to dinghy tow:
1. Position the vehicle being towed
behind the tow vehicle, facing
forward and on a level surface.
2. Securely attach the vehicle
being towed to the tow vehicle.
3. Apply the parking brake and
start the engine.
4. Shift the transfer case to
N (Neutral). See “ Shifting into
N (Neutral) ” under Four-Wheel
Drive on page 9-40 for the
proper procedure. Check that
the vehicle is in N (Neutral) by shifting the transmission to
R (Reverse) and then to D
(Drive). There should be no
movement of the vehicle while
shifting.
5. With the transmission in D
(Drive), turn the ignition to ACC/
ACCESSORY.
{ CautionFailure to disconnect the negative
battery cable or to have it contact
the terminals can cause damage
to the vehicle.
6. Disconnect the negative battery
cable at the battery and secure
the nut and bolt. Cover the
negative battery post with a
non-conductive material to
prevent any contact with the
negative battery terminal.
7. Shift the transmission to
P (Park). { CautionIf the steering column is locked,
vehicle damage may occur.
8. Move the steering wheel to
make sure the steering column
is unlocked.
9. Release the parking brake.
10. Keep the ignition key in the
towed vehicle in ACC/
ACCESSORY to prevent the
steering column from locking.
Disconnecting the Towed Vehicle
Before disconnecting the towed
vehicle:
1. Park on a level surface.
2. Set the parking brake, shift the
transmission to P (Park), and
move the ignition key to OFF.
3. Connect the battery.
4. Apply the brake pedal.

Black plate (8,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
i-8 INDEX Messages
Airbag System . . . . . . . . . . . . . . . . 5-37
Battery Voltage and
Charging . . . . . . . . . . . . . . . . . . . . 5-31
Brake System . . . . . . . . . . . . . . . . 5-32
Compass . . . . . . . . . . . . . . . . . . . . . 5-32
Door Ajar . . . . . . . . . . . . . . . . . . . . . 5-33
Engine Cooling System . . . . . . . 5-33
Engine Oil . . . . . . . . . . . . . . . . . . . . 5-34
Engine Power . . . . . . . . . . . . . . . . 5-34
Fuel System . . . . . . . . . . . . . . . . . . 5-35
Key and Lock . . . . . . . . . . . . . . . . . 5-35
Lamp . . . . . . . . . . . . . . . . . . . . . . . . . 5-35
Object Detection System . . . . . 5-35
Ride Control System . . . . . . . . . . 5-36
Safety Belt . . . . . . . . . . . . . . . . . . . . 5-37
Security . . . . . . . . . . . . . . . . . . . . . . 5-38
Steering System . . . . . . . . . . . . . . 5-38
Tire . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-38
Transmission . . . . . . . . . . . . . . . . . 5-39
Vehicle . . . . . . . . . . . . . . . . . . . . . . . 5-31
Vehicle Reminder . . . . . . . . . . . . . 5-41
Vehicle Speed . . . . . . . . . . . . . . . . 5-42
Washer Fluid . . . . . . . . . . . . . . . . . 5-42 Mirrors
Automatic Dimming . . . . . . . . . . . 2-17
Automatic Dimming
Rearview . . . . . . . . . . . . . . . . . . . . 2-19
Blind Spot . . . . . . . . . . . . . . . . . . . . 2-17
Convex . . . . . . . . . . . . . . . . . . . . . . . 2-14
Folding . . . . . . . . . . . . . . . . . . . . . . . 2-16
Heated . . . . . . . . . . . . . . . . . . . . . . . 2-17
Power . . . . . . . . . . . . . . . . . . . . . . . . 2-14
Tilt in Reverse . . . . . . . . . . . . . . . . 2-18
Trailer Tow . . . . . . . . . . . . . . . . . . . . 2-14
Mirrors, Interior Rearview . . . . . . 2-19
Monitor System, Tire
Pressure . . . . . . . . . . . . . . . . . . . . 10-61
N Navigation
OnStar ®
. . . . . . . . . . . . . . . . . . . . . . 14-3
New Vehicle Break-In . . . . . . . . . . 9-23
Noise Control System . . . . . . . . 10-32 O Object Detection System
Messages . . . . . . . . . . . . . . . . . . . . 5-35
Odometer . . . . . . . . . . . . . . . . . . . . . . 5-11
Trip . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-11
Off-Road . . . . . . . . . . . . . . . . . . . . . . . 9-6
Driving . . . . . . . . . . . . . . . . . . . . . . . . . 9-6
Recovery . . . . . . . . . . . . . . . . . . . . . . 9-5
Oil
Engine . . . . . . . . . . . . . . . . . . . . . . . . 10-8
Engine Oil Life System . . . . . .10-11
Engine Oil Pressure
Gauge . . . . . . . . . . . . . . . . . . . . . . 5-12
Messages . . . . . . . . . . . . . . . . . . . . 5-34
Pressure Light . . . . . . . . . . . . . . . . 5-25
Older Children, Restraints . . . . . 3-30
Online Owner Center . . . . . . . . . . 13-4
OnStar . . . . . . . . . . . . . . . . . . . . . . . 13-15
OnStar ®
System, In Brief . . . . . . . . . . . . . . 1-22
OnStar ®
Additional
Information . . . . . . . . . . . . . . . . . . . 14-6
OnStar ®
Connections . . . . . . . . . . 14-4
OnStar ®
Emergency . . . . . . . . . . . 14-2
OnStar ®
Navigation . . . . . . . . . . . . 14-3
OnStar ®
Overview . . . . . . . . . . . . . 14-1