ignition GMC SIERRA 2020 Service Manual

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Climate Controls 181
or passenger side temperature
display shows the temperature
setting increasing or decreasing.
SYNC :Press to link the passenger
temperature setting to the driver
setting. The SYNC indicator light will
turn on. When the passenger setting
is adjusted, the SYNC indicator light
will turn off.
Air Delivery Mode Control : Press
z,Y, or[to change the
direction of the airflow. Any
combination of the three controls
can be selected. An indicator light
comes on in the selected mode
button.
Changing the mode cancels the
automatic operation and the system
goes into manual mode. Press
AUTO to return to automatic
operation.
To change the current mode, select
one or more of the following:
z: Air is directed to the
windshield, outboard a/c outlets,
and side window outlets.
Y: Air is directed to the a/c outlets.
[:Air is directed to the floor
outlets, with some air directed to the
windshield, outboard a/c outlets,
and side window outlets.
0MAX : Air is directed to the
windshield and the fan runs at a
higher speed if not already above a
medium fan speed. This mode
overrides the previous mode
selected and clears fog or frost from
the windshield more quickly. When
the control is pressed again, the
system returns to the previous mode
setting and fan speed.
For best results, clear all snow and
ice from the windshield before
defrosting.
@: Press to turn on recirculation.
An indicator light comes on. Air is
recirculated to quickly cool the
inside of the vehicle. It can also be
used to help reduce outside air and
odors that enter the vehicle. Avoid using recirculation for long
periods of time in cold or damp
conditions. Using recirculation in
cold or damp conditions can result
in window fogging.
A/C :
Press to turn the air
conditioning on or off. An indicator
light comes on to show that the air
conditioning is enabled. If the fan is
turned off, the air conditioner will not
run. The A/C light will stay on even
if the outside temperatures are
below freezing.
Rear Window Defogger
1REAR : If equipped, press to
turn the rear window defogger on or
off. An indicator light on the button
comes on to show that the rear
window defogger is on.
The rear window defogger only
works when the engine is running.
The defogger turns off if the ignition
is turned off or to ACC/
ACCESSORY.
If equipped with heated outside
mirrors, press
fto turn them on or
off. See Heated Mirrors 044.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 185
Driving and
Operating
Driving Information
Driving for Better FuelEconomy . . . . . . . . . . . . . . . . . . . . 186
Distracted Driving . . . . . . . . . . . . 187
Defensive Driving . . . . . . . . . . . . . 187
Drunk Driving . . . . . . . . . . . . . . . . . 188
Control of a Vehicle . . . . . . . . . . . 188
Braking . . . . . . . . . . . . . . . . . . . . . . . 188
Steering . . . . . . . . . . . . . . . . . . . . . . 188
Off-Road Recovery . . . . . . . . . . . 190
Loss of Control . . . . . . . . . . . . . . . 190
Off-Road Driving . . . . . . . . . . . . . 191
Driving on Wet Roads . . . . . . . . 196
Hill and Mountain Roads . . . . . 197
Winter Driving . . . . . . . . . . . . . . . . 197
If the Vehicle Is Stuck . . . . . . . . 199
Vehicle Load Limits . . . . . . . . . . . 200
Truck-Camper Loading Information . . . . . . . . . . . . . . . . . . 206
Starting and Operating
New Vehicle Break-In . . . . . . . . . 208
Ignition Positions (KeylessAccess) . . . . . . . . . . . . . . . . . . . . . 208 Ignition Positions (Key
Access) . . . . . . . . . . . . . . . . . . . . . 210
Starting the Engine . . . . . . . . . . . 212
Stop/Start System . . . . . . . . . . . . 213
Engine Heater . . . . . . . . . . . . . . . . 215
Retained Accessory Power (RAP) . . . . . . . . . . . . . . . . 217
Shifting Into Park . . . . . . . . . . . . . 217
Shifting out of Park . . . . . . . . . . . 218
Parking over Things That Burn . . . . . . . . . . . . . . . . . . . 219
Active Fuel Management . . . . . 219
Extended Parking . . . . . . . . . . . . 219
Engine Exhaust
Engine Exhaust . . . . . . . . . . . . . . 220
Running the Vehicle While Parked . . . . . . . . . . . . . . . . . . . . . . 220
Automatic Transmission
Automatic Transmission . . . . . . 221
Manual Mode . . . . . . . . . . . . . . . . . 224
Tow/Haul Mode . . . . . . . . . . . . . . . 226
Drive Systems
Four-Wheel Drive . . . . . . . . . . . . . 227
Brakes
Electric Brake Boost . . . . . . . . . . 232
Antilock BrakeSystem (ABS) . . . . . . . . . . . . . . . 232
Electric Parking Brake . . . . . . . . 233 Brake Assist . . . . . . . . . . . . . . . . . . 234
Hill Start Assist (HSA) . . . . . . . . 235
Ride Control Systems
Traction Control/Electronic
Stability Control . . . . . . . . . . . . . 235
Hill Descent Control (HDC) . . . 237
Driver Mode Control . . . . . . . . . . 238
Limited-Slip Differential . . . . . . . 242
Locking Rear Axle . . . . . . . . . . . . 243
Cruise Control
Cruise Control . . . . . . . . . . . . . . . . 243
Adaptive Cruise Control (1500 Series) . . . . . . . . . . . . . . . . . . . . . . 245
Driver Assistance Systems
Driver Assistance Systems . . . 256
Assistance Systems forParking or Backing . . . . . . . . . . 257
Assistance Systems for Driving . . . . . . . . . . . . . . . . . . . . . . 268
Forward Collision Alert (FCA) System . . . . . . . . . . . . . . . . . . . . . . 268
Automatic Emergency Braking (AEB) . . . . . . . . . . . . . . . 270
Front Pedestrian Braking (FPB) System (1500
Series) . . . . . . . . . . . . . . . . . . . . . . 272
Side Blind Zone Alert (SBZA) . . . . . . . . . . . . . . . . 274

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
196 Driving and Operating
Caution
Do not drive through standing
water if it is deep enough to cover
the wheel hubs, axles, or exhaust
pipe. Deep water can damage the
axle and other vehicle parts.
If the standing water is not too deep,
drive through it slowly. At faster
speeds, water can get into the
engine and cause it to stall. Stalling
can occur if the exhaust pipe is
under water. Do not turn off the
ignition when driving through water.
If the exhaust pipe is under water,
the engine will not start. When going
through water, the brakes get wet
and it may take longer to stop. See
“Driving on Wet Roads” later in this
section.
After Off-Road Driving
Remove any brush or debris that
has collected on the underbody or
chassis, or under the hood. These
accumulations can be a fire hazard.
Re-install underbody air deflector
and air dam if removed. After operation in mud or sand,
have the brake linings cleaned and
checked. These substances can
cause glazing and uneven braking.
Check the body structure, driveline,
steering, suspension, wheels, tires,
and exhaust system for damage and
check the fuel lines and cooling
system for any leakage.
More frequent maintenance service
is required. See the
Maintenance
Schedule 0442.
Driving on Wet Roads
Rain and wet roads can reduce
vehicle traction and affect your
ability to stop and accelerate.
Always drive slower in these types
of driving conditions and avoid
driving through large puddles and
deep-standing or flowing water.
{Warning
Wet brakes can cause crashes.
They might not work as well in a
quick stop and could cause
pulling to one side. You could
lose control of the vehicle.
After driving through a large
puddle of water or a car/vehicle
wash, lightly apply the brake
pedal until the brakes work
normally.
Flowing or rushing water creates
strong forces. Driving through
flowing water could cause the
vehicle to be carried away. If this
happens, you and other vehicle
occupants could drown. Do not
ignore police warnings and be
very cautious about trying to drive
through flowing water.
Hydroplaning
Hydroplaning is dangerous. Water
can build up under the vehicle's
tires so they actually ride on the
water. This can happen if the road is

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 197
wet enough and you are going fast
enough. When the vehicle is
hydroplaning, it has little or no
contact with the road.
There is no hard and fast rule about
hydroplaning. The best advice is to
slow down when the road is wet.
Other Rainy Weather Tips
Besides slowing down, other wet
weather driving tips include:
.Allow extra following distance.
. Pass with caution.
. Keep windshield wiping
equipment in good shape.
. Keep the windshield washer fluid
reservoir filled.
. Have good tires with proper
tread depth. See Tires0379.
. Turn off cruise control.
Hill and Mountain Roads
Driving on steep hills or through
mountains is different than driving
on flat or rolling terrain. Tips include: .
Keep the vehicle serviced and in
good shape.
. Check all fluid levels and brakes,
tires, cooling system, and
transmission.
. Shift to a lower gear when going
down steep or long hills.
{Warning
Using the brakes to slow the
vehicle on a long downhill slope
can cause brake overheating, can
reduce brake performance, and
could result in a loss of braking.
Shift the transmission to a lower
gear to let the engine assist the
brakes on a steep downhill slope.
{Warning
Coasting downhill in N (Neutral)
or with the ignition off is
dangerous. This can cause
overheating of the brakes and
(Continued)
Warning (Continued)
loss of steering assist. Always
have the engine running and the
vehicle in gear.
. Drive at speeds that keep the
vehicle in its own lane. Do not
swing wide or cross the
center line.
. Be alert on top of hills;
something could be in your lane
(e.g., stalled car, crash).
. Pay attention to special road
signs (e.g., falling rocks area,
winding roads, long grades,
passing or no-passing zones)
and take appropriate action.
Winter Driving
Driving on Snow or Ice
Snow or ice between the tires and
the road creates less traction or
grip, so drive carefully. Wet ice can
occur at about 0 °C (32 °F) when

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
208 Driving and Operating
Starting and
Operating
New Vehicle Break-In
Caution
The vehicle does not need an
elaborate break-in. But it will
perform better in the long run if
you follow these guidelines:. Keep the vehicle speed at
88 km/h (55 mph) or less for
the first 805 km (500 mi).
. Do not drive at any one
constant speed, fast or slow,
for the first 805 km (500 mi).
Do not make full-throttle
starts. Avoid downshifting to
brake or slow the vehicle.
. Avoid making hard stops for
the first 322 km (200 mi) or
so. During this time the new
brake linings are not yet
broken in. Hard stops with
new linings can mean
(Continued)
Caution (Continued)
premature wear and earlier
replacement. Follow this
breaking-in guideline every
time you get new brake
linings.
. Do not tow a trailer during
break-in. See Trailer Towing
0 292 for the trailer towing
capabilities of the vehicle
and more information.
Following break-in, engine speed
and load can be gradually
increased.
Ignition Positions
(Keyless Access)
Vehicles equipped with Keyless
Access have pushbutton starting.
The Remote Keyless Entry (RKE)
transmitter must be in the vehicle for
the system to operate. If the
pushbutton start is not working, the
vehicle may be near a strong radio
antenna signal causing interference
to the Keyless Access system. See
Remote Keyless Entry (RKE)
System Operation (Key Access)
0 13 or

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 209
Remote Keyless Entry (RKE)
System Operation (Keyless Access)
015.
To shift out of P (Park), the ignition
must be on or in Service Mode, and
the brake pedal must be applied.
{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.
Stopping the Engine/LOCK/
OFF (No Indicator Lights) : When
the vehicle is stopped, press
ENGINE START/STOP once to turn
the engine off.
If the vehicle is in P (Park), the
ignition will turn off, and Retained
Accessory Power (RAP) will remain
active. See Retained Accessory
Power (RAP) 0217. If the vehicle is not in P (Park), the
ignition will return to ACC/
ACCESSORY and display the
message SHIFT TO PARK in the
Driver Information Center (DIC).
When the vehicle is shifted into
P (Park), the ignition system will
turn off.
The vehicle may have an electric
steering column lock. The lock is
activated when the ignition is turned
off and driver door is opened.
A sound may be heard as the lock
actuates or releases. The steering
column lock may not release with
the wheels turned off center. If this
happens, the vehicle may not start.
Move the steering wheel from left to
right while attempting to start the
vehicle. If this does not work, the
vehicle needs service.
Unless an emergency exists, 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. If the vehicle cannot be pulled
over, and must be shut off
while driving, press and hold
ENGINE START/STOP button
for longer than two seconds,
or press twice in five seconds.
2. Brake using a firm and steady pressure. Do not pump the
brakes repeatedly. This may
deplete power assist, requiring
increased brake pedal force.
3. 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.
4. Come to a complete stop, shift to P (Park) with an automatic
transmission, or Neutral with a
manual transmission, and
make sure engine is off. On
vehicles with an automatic
transmission, the shift lever
must be in P (Park) to turn the
ignition off.
5. Set the parking brake. See Electric Parking Brake 0233.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
210 Driving and Operating
{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.
ACC/ACCESSORY (Amber
Indicator Light) : This mode allows
some electrical accessories to be
used when the engine is off. For a
manual transmission, set the
parking brake before putting the
ignition in ACC/ACCESSORY.
With the ignition off, pressing the
ENGINE START/STOP button one
time without the brake pedal applied
will place the ignition system in
ACC/ACCESSORY.
The ignition will switch from ACC/
ACCESSORY to off after
five minutes to prevent battery
rundown. ON/RUN/START (Green Indicator
Light) :
This mode is for driving and
starting. With the ignition off, and
the brake pedal applied, pressing
ENGINE START/STOP button once
will turn the ignition on. Once engine
cranking begins, release the button.
Engine cranking will continue until
the engine starts. See Starting the
Engine 0212.
Service Mode
This power mode is available for
service and diagnostics, and to
verify the proper operation of the
malfunction indicator lamp as may
be required for emission inspection
purposes. With the vehicle off, and
the brake pedal not applied,
pressing and holding the ENGINE
START/STOP button for more than
five seconds will place the vehicle in
Service Mode. The instruments and
audio systems will operate as they
do when the ignition is on, but the
vehicle will not be able to be driven.
The engine will not start in Service
Mode. Press the ENGINE START/
STOP button again to turn the
ignition off.
Ignition Positions (Key
Access)
0. Stopping the Engine/LOCK/OFF
1. ACC/ACCESSORY
2. ON/RUN
3. START
The ignition switch has four
positions.
To shift out of P (Park), the ignition
must be ON/RUN and the brake
pedal must be applied.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 211
0 (Stopping the Engine/LOCK/
OFF) :This position turns off the
vehicle. It also locks the ignition, the
transmission, and the steering
column, if equipped with a locking
steering column.
To turn off the vehicle:
1. Make sure that the vehicle is stopped.
2. Shift to P (Park).
3. Continue to hold the brake pedal, then set the parking
brake. See Electric Parking
Brake 0233. 4. Push the key all the way in
toward the steering column,
then turn the key to
LOCK/OFF.
5. Remove the key.
6. Release the brake pedal.
See your dealer if the key can be
removed in any other position.
Retained Accessory Power (RAP)
will remain active. See Retained
Accessory Power (RAP) 0217.
A warning chime will sound when
the driver door is opened and the
key is in the ignition.
If equipped with a locking steering
column, the steering can bind with
the front wheels turned off center,
which may prevent key rotation out
of LOCK/OFF. If this happens, move
the steering wheel from right to left
while turning the key to ACC/
ACCESSORY. If this does not work,
then the vehicle needs service.
{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, turn off the vehicle
only in an emergency.
In an emergency, if the vehicle
cannot be pulled over and must be
turned off while driving: 1. Push the key all the way in toward the steering column,
then turn the key to ACC/
ACCESSORY.
2. Brake using firm and steady pressure. Do not pump the
brakes repeatedly. This may
deplete power assist, requiring
increased brake pedal force.
3. Shift the vehicle to N (Neutral). This can be done while the
vehicle is moving. Continue
braking and steer the vehicle to
a safe location.
4. Come to a complete stop.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
212 Driving and Operating
5. Shift to P (Park) with anautomatic transmission, or stay
in Neutral with a manual
transmission.
6. Push the key all the way in toward the steering column (1),
then turn the ignition to
LOCK/OFF (2).
7. Set the parking brake. See Electric Parking Brake 0233.
8. Remove the key.
9. Release the brake pedal.
Caution
Use the correct key, make sure it
is all the way in —or pushed all
the way in toward the steering
column when turning off the
vehicle —and turn it only with
your hand.
1 (ACC/ACCESSORY) : This
position allows features such as the
infotainment system to operate
while the vehicle is off. It also
unlocks the steering column, if equipped with a locking steering
column. Use this position if the
vehicle must be pushed or towed.
See
Retained Accessory Power
(RAP) 0217.
From ON/RUN, push the key all the
way in toward the steering column,
then turn the key to ACC/
ACCESSORY.
If the key is left in ACC/
ACCESSORY with the engine off,
the battery could drain and the
vehicle may not start.
A warning chime will sound when
the driver door is opened and the
key is in the ignition.
2 (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.
If the key is left in ON/RUN with the
engine off, the battery could drain
and the vehicle may not start.
3 (START) :
This is the position that
starts the engine. When the engine
starts, release the key. The ignition
returns to ON/RUN for driving.
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
0 322.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 213
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. For Key Access vehicles, turnthe ignition key to START.
When the engine starts, let go
of the key.
For Keyless Access vehicles,
the RKE transmitter must be in
the vehicle. Press ENGINE
START/STOP with the brake
pedal applied. When the
engine begins cranking, let go
of the button.
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
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
or ENGINE START/STOP for
up to a maximum of
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 or
button 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.
Stop/Start System
If equipped, the Stop/Start system
will shut off the engine to help
conserve fuel. It has components
designed for the increased number
of starts.