2020 GMC SIERRA DENALI ECO mode

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
138 Instruments and Controls
Caution
Modifications to the engine,
transmission, exhaust, intake,
or fuel system, or the use of
replacement tires that do not
meet the original tire
specifications, can cause this light
to come on. This could lead to
costly repairs not covered by the
vehicle warranty. This could also
affect the vehicle’s ability to pass
an Emissions Inspection/
Maintenance test. See
Accessories and Modifications
0329.
If the light is flashing : A
malfunction has been detected that
could damage the emission control
system and increase vehicle
emissions. Diagnosis and service
may be required.
To help prevent damage, reduce
vehicle speed and avoid hard
accelerations and uphill grades. If towing a trailer, reduce the
amount of cargo being hauled as
soon as possible.
If the light continues to flash, find a
safe place to park. Turn the vehicle
off and wait at least 10 seconds
before restarting the engine. If the
light is still flashing, follow the
previous guidelines and see your
dealer for service as soon as
possible.
If the light is on steady :
A
malfunction has been detected.
Diagnosis and service may be
required.
Check the following:
. If fuel has been added to the
vehicle using the capless funnel
adapter, make sure that it has
been removed. See “Filling the
Tank with a Portable Gas Can”
under Filling the Tank (Pickup
Model) 0283 or
Filling the Tank (Chassis Cab
Model) 0285. The diagnostic
system can detect if the adapter
has been left installed in the
vehicle, allowing fuel to evaporate into the atmosphere.
A few driving trips with the
adapter removed may turn off
the light.
. Poor fuel quality can cause
inefficient engine operation and
poor driveability, which may go
away once the engine is warmed
up. If this occurs, change the
fuel brand. It may require at
least one full tank of the proper
fuel to turn the light off. See
Recommended Fuel (Except
6.2L V8 Engine) 0280 or
Recommended Fuel (6.2L
V8 Engine) 0281.
If the light remains on, see your
dealer.
Emissions Inspection and
Maintenance Programs
If the vehicle requires an Emissions
Inspection/Maintenance test, the
test equipment will likely connect to
the vehicle's Data Link
Connector (DLC).

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
170 Lighting
Turn and Lane-Change
Signals
An arrow on the instrument cluster
flashes in the direction of the turn or
lane change.
Move the turn signal lever all the
way up or down to signal a turn.
Partially raise or lower the lever for
less than one second until the arrow
starts to flash to signal a lane
change. This causes the turn
signals to automatically flash three
times. It will flash six times if Tow/
Haul Mode is active. Holding the
turn signal lever for more than
one second will cause the turn
signals to flash until the lever is
released.The lever returns to its starting
position whenever it is released.
If after signaling a turn or a lane
change the arrows flash rapidly or
do not come on, a signal bulb could
be burned out. If equipped with LED
turn signals, see your dealer.
Replace any burned out bulbs. If a
bulb is not burned out, check the
fuse. See
Fuses and Circuit
Breakers 0370.
Turn Signal On Chime
If the turn signal is left on for more
than 1.2 km (0.75 mi), a chime
sounds at each flash of the turn
signal. A message may appear in
the Driver Information Center (DIC).
See Vehicle Messages 0155. To
turn the chime and message off,
move the turn signal lever to the off
position.
Fog Lamps
If equipped, the fog lamp control is
near the exterior lamp control to the
left of the steering column.
The ignition must be on for the fog
lamps to come on.
#: Press to turn the fog lamps on
or off. A light will come on in the
instrument cluster.
When the fog lamps are turned on,
the parking lamps automatically
turn on.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Climate Controls 177
Climate Controls
Climate Control Systems
Climate Control Systems . . . . . 177
Dual Automatic ClimateControl System . . . . . . . . . . . . . 179
Air Vents
Air Vents . . . . . . . . . . . . . . . . . . . . . 182
Maintenance
Passenger Compartment AirFilter . . . . . . . . . . . . . . . . . . . . . . . . 183
Service . . . . . . . . . . . . . . . . . . . . . . . 184
Climate Control Systems
The heating, cooling, and ventilation in the vehicle can be controlled with this
system.
1. Fan Control
2. MAX Defrost
3. Air Delivery Mode Controls
4. A/C (Air Conditioning)
5. TEMP (Temperature Control)
6. Recirculation
7. Rear Window Defogger (If
Equipped) or Heated Mirrors (If
Equipped)9:Turn clockwise or
counterclockwise to increase or
decrease the fan speed. Turn the
knob all the way counterclockwise
to turn the fan off.
TEMP : Turn clockwise or
counterclockwise to increase or
decrease the temperature inside the
vehicle.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
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) . . . . . . . . . . . . . . . . 216
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 . . . . . . . . . . . . . . . 227
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 . . . . . . . . . . . . 242
Cruise Control
Cruise Control . . . . . . . . . . . . . . . . 243
Adaptive Cruise Control (1500 Series) . . . . . . . . . . . . . . . . . . . . . . 245
Driver Assistance Systems
Driver Assistance Systems . . . 255
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 - 8/27/19
186 Driving and Operating
Lane Change Alert (LCA) . . . . . 274
Lane Departure Warning(LDW) (2500/3500
Series) . . . . . . . . . . . . . . . . . . . . . . 276
Lane Keep Assist (LKA) (1500
Series) . . . . . . . . . . . . . . . . . . . . . . 278
Fuel
Top Tier Fuel . . . . . . . . . . . . . . . . . 280
Recommended Fuel (Except6.2L V8 Engine) . . . . . . . . . . . . . 280
Recommended Fuel (6.2L V8 Engine) . . . . . . . . . . . . . . . . . . 281
Prohibited Fuels . . . . . . . . . . . . . . 281
Fuels in Foreign Countries . . . 281
Fuel Additives . . . . . . . . . . . . . . . . 282
E85 or FlexFuel . . . . . . . . . . . . . . 282
Filling the Tank (Pickup Model) . . . . . . . . . . . . . . . . . . . . . . 283
Filling the Tank (Chassis Cab Model) . . . . . . . . . . . . . . . . . . . . . . 285
Filling a Portable Fuel Container . . . . . . . . . . . . . . . . . . . 286
Trailer Towing
General TowingInformation . . . . . . . . . . . . . . . . . . 287
Driving Characteristics and Towing Tips . . . . . . . . . . . . . . . . . 287
Trailer Towing . . . . . . . . . . . . . . . . 292
Towing Equipment . . . . . . . . . . . . 296 Trailer Sway Control (TSC) . . . 308
Trailering App . . . . . . . . . . . . . . . . 310
Conversions and Add-Ons
Add-On Electrical
Equipment . . . . . . . . . . . . . . . . . . 322
Adding a Snow Plow or Similar Equipment . . . . . . . . . . . . . . . . . . 323
Pickup Conversion to Chassis Cab . . . . . . . . . . . . . . . . 326
Driving Information
Driving for Better Fuel
Economy
Driving habits can affect fuel
mileage. Here are some driving tips
to get the best fuel economy
possible:
. Set the climate controls to the
desired temperature after the
engine is started, or turn them
off when not required.
. Avoid fast starts and accelerate
smoothly.
. Brake gradually and avoid
abrupt stops.
. Avoid idling the engine for long
periods of time.
. When road and weather
conditions are appropriate, use
cruise control.
. Always follow posted speed
limits or drive more slowly when
conditions require.
. Keep vehicle tires properly
inflated.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Driving and Operating 209
to the Keyless Access system. See
Remote Keyless Entry (RKE)
System Operation (Key Access)
013 or
Remote Keyless Entry (RKE)
System Operation (Keyless Access)
0 16.
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) 0216.
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), and make sure
engine is off. The shift lever
must be in P (Park) to turn the
ignition off.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
210 Driving and Operating
5. Set the parking brake. SeeElectric Parking Brake 0233.
{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.
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 - 8/27/19
Driving and Operating 215
Whenhis illuminated, the system
is enabled.
Engine Heater
If equipped, the engine heater can
provide easier starting and better
fuel economy during engine
warm-up in cold weather conditions
at or below −18 °C (0 °F). Vehicles
with an engine heater should be
plugged in at least four hours before
starting. An internal thermostat in
the plug-end of the cord may exist,
which will prevent engine heater
operation at temperatures above
−18 °C (0 °F).
{Warning
Do not plug in the engine block
heater while the vehicle is parked
in a garage or under a carport.
Property damage or personal
injury may result. Always park the
vehicle in a clear open area away
from buildings or structures.
1500 Base Model shown other
models are similar
2500/3500
To Use the Engine Heater
1. Turn off the engine.
2. Check the heater cord fordamage. If it is damaged, do
not use it. See your dealer for
a replacement. Inspect the
cord for damage yearly.
3. 1500 only, remove the engine
heater connector cover by
gently prying with a flat
blade tool.
4. Plug the heater cord into the connector in the front fascia.