wheel GMC SIERRA 2018 Repair Manual

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
258 Driving and Operating
The switch stays in this position
when the engine is running. The
transmission is also unlocked in this
position.
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.
3 (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.
For an eAssist vehicle, see the
Silverado/Sierra eAssist
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
0 336.
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 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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 259
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
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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
262 Driving and Operating
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 (Continued)
Warning (Continued)
is in P (Park). Be sure the transfer
case is in a drive gear. If towing a
trailer, seeDriving Characteristics
and Towing Tips 0303.
1. Hold the brake pedal down, then set the parking brake. See
Parking Brake 0281.
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 (if equipped) is in a drive gear–
not in N (Neutral).
4. Turn the ignition 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
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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 265
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 0262 and
Engine Exhaust 0264.
If parking on a hill and pulling a
trailer, see Driving Characteristics
and Towing Tips 0303.
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 on.
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 0268.
P : This position locks the rear
wheels. Use P (Park) when starting
the engine because the vehicle
cannot move easily.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
266 Driving and Operating
When parked on a hill, 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”underShifting Into
Park 0262
{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 0262 and
Driving Characteristics and
Towing Tips 0303.
{Warning
If equipped with four-wheel drive,
the vehicle will be free to roll if the
transfer case is in N (Neutral),
even when the shift lever is in
P (Park). You or someone else
could be seriously injured. Be
sure the transfer case is in a drive
gear —2
m, 4m, or 4nor set the
parking brake before placing the
transfer case in N (Neutral). See
Shifting Into Park 0262.
R : 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 0247.
N : In this position, the engine does
not connect with the wheels. To
restart the engine when the vehicle
is 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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 271
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 L2 using
Range Selection Mode. This will
limit torque to the wheels and help
to prevent the tires from spinning.
Tow/Haul Mode
Vehicles with an automatic
transmission have a Tow/Haul
Mode. The Tow/Haul Mode adjusts
the transmission shift pattern to
reduce shift cycling. This providesincreased performance, vehicle
control, and enhanced transmission
and engine cooling when driving
down steep hills or mountain
grades, when towing, or when
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.
For an eAssist vehicle, the Stop/
Start function will become
unavailable when Tow/Haul Mode is
active.
For an eAssist vehicle, the
Regenerative Braking functionality is
disabled when using the Tow/Haul
Mode. See the eAssist supplement.
See
Tow/Haul Mode Light 0153 and
Hill and Mountain Roads 0245.
Also see “Tow/Haul Mode” under
Towing Equipment 0325.
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 Mode0268.
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.
If equipped, 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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
272 Driving and Operating
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.
SeeTowing Equipment 0325.
For other forms of grade braking,
see Automatic Transmission 0265
and Cruise Control 0285.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
Do not drive on clean, dry
pavement in 4
mand 4n(if
equipped) for an extended period
of time. These conditions may
cause premature wear on the
vehicle’s powertrain.
Driving on clean, dry pavement in
4
mor 4nmay:
. 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
If equipped with four-wheel drive,
the vehicle will be free to roll if the
transfer case is in N (Neutral),
even when the shift lever is in
P (Park). You or someone else
could be seriously injured. Be
sure the transfer case is in a drive
gear —2
m, 4m, or 4nor set the
parking brake before placing the
transfer case in N (Neutral). See
Shifting Into Park 0262.
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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 273
Shifting into 4nwill turn Traction
Control and StabiliTrak off. See
Traction Control/Electronic Stability
Control 0282.
Manual Transfer Case
Move the lever to shift into and out
of four-wheel drive.
An indicator light comes on when
four-wheel drive is engaged. See
Four-Wheel-Drive Light 0153.
N (Neutral) : Use only when the
vehicle needs to be towed.
See Recreational Vehicle Towing
0 430 orTowing the Vehicle 0430.
2
m(Two-Wheel Drive High) : Use
this setting 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 also 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).
4
m(Four-Wheel Drive High) : Use
this setting 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 between
2
mand 4mwhile the vehicle is
moving. In extremely cold weather,
it may be necessary to stop or slow
the vehicle to shift into 4
m.
Using the Manual Transfer Case
. Use quick motions to shift into or
out of 4
nor N (Neutral).
. Shifting may be harder when the
vehicle is cold, but will return to
normal once warmed up.
. Four-wheel drive reduces fuel
economy.
. Delayed shifts from 4
mto 2mmay
be experienced due to uneven
tire wear, low tire pressure, high
vehicle loading, or cold
temperatures.
Shifting from 2
mto 4m
. Shifts can be made at any
vehicle speed.
. Shift in one continuous motion.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
274 Driving and Operating
.Shifting while the vehicle is in
motion may require that
moderate force be applied to the
shift lever before 4
mcan be
engaged, especially in cold
weather.
. In extremely cold weather, it may
be necessary to slow or stop the
vehicle to shift.
. While in 4
m, the vehicle can be
driven at any posted legal speed
limit.
Shifting In or Out of 4
n
Caution
Shifting the transfer case into 4n
while moving at speeds faster
than 5 km/h (3 mph) may cause
premature wear to the transfer
case, and may cause the gears to
grind.
1. If possible, shift with the vehicle moving 5 km/h (3 mph)
or less. 2. Shift the transmission into
N (Neutral).
3. Shift the transfer case shift lever in one continuous motion.
4. Shifting with the vehicle at a stop may be more difficult. It is
possible that the shift will not
complete and the transfer case
will remain in N (Neutral). This
is normal. To complete the
shift, with the engine running,
shift the transmission to
D (Drive) and back to
N (Neutral), and reattempt the
transfer case shift.
Shifting In or Out of N (Neutral) 1. Have the engine running.
2. Set the parking brake. Press and hold the brake pedal. See
Parking Brake 0281.
3. Place the transmission into N (Neutral).
4. Shift the transfer case lever in one continuous motion into or
out of N (Neutral).
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.
All of the lights will blink on then off
momentarily when the ignition is
turned on. The light that remains on
will indicate the state of the
transfer case.
If the indicator mark on the switch
does not match up with the light
then that likely means the switch
was moved when the ignition
was off.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 275
The indicator mark on the switch
must line up with the indicator light
before a shift can be commanded.
To command a shift rotate the
transfer case switch to the new
desired position. The light will blink
meaning that the shift is in progress.
When the shift is completed the new
position will be illuminated. If the
transfer case can not complete a
shift command, it will go back to its
last chosen setting.
In extreme cold weather it may be
necessary to slow or stop the
vehicle to shift from 2
mto 4m.
Delayed shifts from 4
mto 2mmay be
experienced due to uneven tire
wear, low tire pressure, high vehicle
loading, or cold temperatures.
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) :
Use only when the
vehicle needs to be towed. See
Recreational Vehicle Towing 0430
or Towing the Vehicle 0430.
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 0282.
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.
Shifting Into 4
n
When 4nis engaged, vehicle speed
should be kept below 72 km/h
(45 mph).
1. The ignition must be on and the vehicle must be stopped or
moving less than 5 km/h
(3 mph) with the transmission
in N (Neutral). It is best for the
vehicle to be moving
1.6 to 3.2 km/h (1 to 2 mph).