2020 GMC SIERRA ignition

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
308 Driving and Operating
To determine whether the electrical
fault is on the vehicle side or trailer
side of the trailer wiring harness
connection:1. Disconnect the trailer wiring harness from the vehicle.
2. Turn the ignition off.
3. Wait 10 seconds, then turn the ignition back to RUN.
4. If the CHECK TRAILER WIRING message reappears,
the electrical fault is on the
vehicle side.
If the CHECK TRAILER WIRING
message only reappears when
connecting the trailer wiring harness
to the vehicle, the electrical fault is
on the trailer side.
SERVICE TRAILER BRAKE
SYSTEM: This message will display
when there is a problem with the
ITBC system. If this message
continues over multiple ignition
cycles, have the vehicle serviced.
If either the CHECK TRAILER
WIRING or SERVICE TRAILER
BRAKE SYSTEM message displays while driving, the ITBC system may
not be fully functional or may not
function at all. When traffic
conditions allow, carefully pull the
vehicle over to the side of the road
and turn the ignition off. Check the
wiring connection to the trailer and
turn the ignition back on. If either of
these messages continues, either
the vehicle or trailer needs service.
A GM dealer may be able to
diagnose and repair problems with
the trailer. However, any diagnosis
and repair of the trailer is not
covered under the vehicle warranty.
Contact your trailer dealer for
assistance with trailer repairs and
trailer warranty information.
Trailer Sway
Control (TSC)
Vehicles with StabiliTrak/Electronic
Stability Control (ESC) have a
Trailer Sway Control (TSC) feature.
Trailer sway is unintended
side-to-side motion of a trailer while
towing. If the vehicle is towing a
trailer and the TSC detects that
sway is increasing, the vehiclebrakes are selectively applied at
each wheel, to help reduce
excessive trailer sway. If equipped
with the Integrated Trailer Brake
Control (ITBC) system, and the
trailer has an electric brake system,
StabiliTrak/ESC may also apply the
trailer brakes.If TSC is enabled, the Traction
Control System (TCS)/StabiliTrak/
ESC warning light will flash on the
instrument cluster. Reduce vehicle
speed by gradually removing your
foot from the accelerator. If trailer
sway continues, StabiliTrak/ESC
can reduce engine torque to help

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 311
Touch Stop to stop the test. The test
will automatically end after
one minute and 45 seconds.
The sequence also deactivates
when any of the following occur:
.The ignition is turned off.
. The transmission is shifted out
of P (Park).
. The brake pedal is pressed.
. The turn signal is activated.
. The hazard warning lights are
activated.
Trailering App
If equipped, the Trailering App is on
the Home Page of the infotainment
display.
If equipped this feature allows
profiles for connected trailers to be
created to view status, to store and
track trailer usage information, and
to set up towing assistance
features.
The Trailering App Preview will
appear when the Trailering App is
opened for the first time from the Home Page. Touch GET STARTED
in the Trailering App to go into
the app.
When a trailer is electrically
connected, there will be an option to
create a profile, use a guest profile,
or cancel. After Cancel is selected a
third time, Don’t Remind Me will
display and touching that will turn off
the trailer detection pop-up. To turn
the Trailer Detection Alert on, select
ON in the Settings tab.
When a trailer is electrically
connected and after a Trailer Profile
has been created, the trailer
detection pop-up will appear with a
list of all of the custom Trailer
Profiles made on the vehicle. To
load an existing Trailer Profile,
select one of the Trailer Profiles
listed, or load the Guest Trailer
Profile by selecting GUEST
TRAILER. Touching Cancel,
Accessory/No trailer, or shifting the
vehicle from P (Park), will select
Accessory/No trailer as the active
Trailer Profile and will dismiss the
pop- up.
Create a Trailer Profile
1. Touch Create Profile on the pop-up or touch + Add Trailer
in the Trailering App.
2. Create a name for the trailer.
3. Select the hitch type. A checklist profile will be
created based on the type
selected.
4. Select the trailer type.
A pop-up will indicate the setup is
complete. Touch DONE to complete
the process or touch TRAILER
FEATURE SETUP to set up the
Tow/Haul Mode reminder, Trailer
Tire Pressure Monitoring System,
if equipped, maintenance reminders,
or towing assistance, if equipped.
Import a Trailer Profile
A trailer profile saved to an OnStar
account can be imported to the
vehicle. 1. Touch Import Profile on the pop-up.
2. Select a trailer profile from the list.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 315
Light, Reverse Lights, and Electric
Brakes, if equipped), the view will
display OK.
Connection Problem
If any of the trailer connections are
not detected, a message about the
connection issue will appear on the
Driver Information Center (DIC). The
infotainment display will also show
the connection issue in the
Connection Status view.
Diagnose View
Touch Diagnose to see more
information about the connection
problem.
This view will display the names of
the trailer connector pins, a graphic
of the trailer connector, and a
graphic of the back of the trailer.
Any connector pin that failed will be
amber color, and the location of the
corresponding connection will be
highlighted on the graphic of the
back of the trailer.The Running Lights connection may
not detect partial outages. Activate
the light test to check all trailer
lamps. See
“Light Test”following.
If the trailer is not equipped with
reverse lights or electric brakes and
you are receiving failure messages
in the DIC or on this view, turn off
the Reverse Lights Alert or the
Electric Brakes Alert setting in the
trailer ’s profile page.
Light Test
Touch Start Light Test to cycle the
trailer lights on and off to determine
if they are working. The test follows
this sequence: 1. The running lights turn on first and remain on throughout the
sequence.
2. The brake lights turn on for about two seconds.
3. The left turn signal light flashes three times.
4. The right turn signal light flashes three times. 5. The reverse lights turn on for
about two seconds.
6. Steps 2–5 repeat for approximately one minute and
45 seconds, or until the test
deactivates.
Touch Stop to stop the test. The test
will automatically end after
one minute and 45 seconds.
The sequence also deactivates
when any of the following occur:
. The ignition is turned off.
. The transmission is shifted out
of P (Park).
. The brake pedal is pressed.
. The turn signal is activated.
. The hazard warning lights are
activated.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
316 Driving and Operating
Trailer
1. Trailer Tire Pressure/Temperature
2. Mileage of Trailer
Mileage
The mileage accumulated while this
Trailer Profile is active will display.
Touch mileage to edit.
Tire Pressure and Temperature
If the TTPMS sensor-to-vehicle
learn process was completed, the
status view will display the current
tire pressure and temperature of the
trailer tires related to the active Trailer Profile. If a tire’
s pressure is
low or high, the color of the
pressure value will be amber. If a
sensor malfunctions, the values are
dashed lines. If the screen displays
“Service Tire Pressure Monitoring
System”, the vehicle needs to be
taken to a dealer for service.
Maintenance
1. List of Maintenance
Reminders
2. Add a New Maintenance Reminder
The Maintenance Status view
displays reminders. Touch a
reminder to edit.
Touch + New Maintenance
Reminder to go to the Select New
Reminder view.
The progress bar turns yellow when
the maintenance item reaches 90%
complete.
The progress bar turns red when
the maintenance item reaches
100% complete.
Maintenance Notifications
.Touch Service Complete to reset
the maintenance reminder.
. Touch Remind Me Later to delay
the reminder.
. Touch X next to Upcoming Alerts
(90%) to dismiss the alert. It will
not appear again.
. Touch X next to Maintenance
Due (100%) to delay the alert to
the next ignition cycle.
Always follow all of the maintenance
instructions that came with your
trailer.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
318 Driving and Operating
associated with Custom Trailer
Profiles in addition to default
checklists.
Trailers View
Touch the Trailers tab to view,
activate, create, edit, or delete
Trailer Profiles.
If a trailer is connected, touch the
Trailer Profile name to activate a
Trailer Profile.
There can be up to five Custom
Trailer Profiles on the vehicle.
The Custom Trailer Profiles and
Guest Trailer are in order of the
most frequently used.
All personalization features are
based on the settings for each
driver in vehicle personalization.
The list of Trailer Profiles is based
on vehicle personalization settings.
Guest Trailer
If the Guest Trailer Profile is the
active Trailer Profile, trailer
detection, connections status, theft,
and the Tow/Haul reminder alerts
can be sent. The system will nottrack total mileage or fuel economy,
but the system will track trip mileage
and fuel economy if the Guest
Trailer Profile is active. The Trailer
Tire Pressure Monitoring System or
maintenance reminders cannot be
set up for a Guest Trailer Profile.
The Guest Trailer Profile cannot be
edited.
Touch
pto learn more about the
Guest Trailer option.
No Trailer Connected
When there is no trailer connected,
Trailer Profiles cannot be activated
but most options can be edited.
Trailer Brake Gain Memory
The system can memorize the brake
gain setting of a Trailer Profile or a
Guest Trailer Profile. When a Trailer
Profile or Guest Trailer Profile is
selected, and a brake gain setting is
set for that Trailer Profile, a quick
notice will appear to indicate that
the system has recalled that
profile’s brake gain setting. If a Trailer Profile is already active
and the brake gain setting had been
set for that Trailer Profile, the quick
notice will trigger whenever the
ignition is turned on.
If there was an error in setting the
brake gain for a Trailer Profile, there
will be a notification. This pop-up
will not appear if the Guest Trailer
Profile is active or if there is no
trailer connected.
Trailer brake gain should be set for
a specific trailering condition and
must be adjusted anytime vehicle
loading, trailer loading, or road
surface conditions change.
Editing a Trailer Profile
Trailer Profile View
Touch to edit any of the following
options in the Trailer Profile view:
.
Trailer Name
. Towing Assistance Setup
. Tire Pressure Setup
. Trailer Maintenance
. Mileage

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/4/19
Driving and Operating 321
Trailer Detection Alert
The Trailer Detection Alert setting
will be on by default. Turn it off to
disable the Trailer Detection pop-up
from displaying when a trailer is
connected. The Guest Trailer Profile
will become the active Trailer
Profile, unless another Trailer Profile
is selected manually through the
Trailering App. If this setting is
disabled while a Custom Trailer
Profile is active, that Trailer Profile
will remain the active profile until the
trailer is disconnected.
Maintenance Alerts
Touch Maintenance Alerts to view
the Maintenance Alerts settings
page. These alerts are based on the
Trailer Profile, so the settings for
each Trailer Profile must be turned
on or off. Touch a profile to view
more information or adjust the
setting for that profile.
The setting will be on by default for
each profile. All Maintenance Alerts
for that active Trailer Profile will be
received.Turn a setting off to not receive any
of the Maintenance Alerts when that
Trailer Profile is active.
Theft Alert
A theft alert can be set if a trailer is
connected and the alert is enabled.
When the trailer is disconnected
and the vehicle is off, an alarm will
sound.
Touch Theft Alert in Settings to view
the Theft Alert settings page. These
alerts are based on the Trailer
Profile, so the settings for each
Trailer Profile must be turned on or
off. Touch a profile to view more
information or adjust the setting for
that profile.
This setting will be off by default for
each Trailer Profile, including the
Guest Trailer Profile.
A smartphone will receive a
notification that the trailer related to
the selected Trailer Profile is
disconnected from the vehicle, if the
setting is on for the active Trailer
Profile, the vehicle has an OnStar or
connected service plan and thesmartphone number has been
added to the account for this
notification.
If the setting is turned off for a given
Trailer Profile, the smartphone will
not receive this security notification
even if the Trailer Profile is active.
Tow/Haul Mode Reminder
This is a reminder to turn on the
Tow/Haul Mode when towing a
trailer. See
Tow/Haul Mode 0226.
Touch Tow/Haul Mode Reminder in
Settings to view the Tow/Haul Mode
Reminder settings page. These
alerts are based on the Trailer
Profile, so the settings for each
Trailer Profile must be turned on or
off. Touch a profile to view more
information or to adjust the setting
for that profile.
This setting will default to OFF for
each Trailer Profile, including the
Guest Trailer Profile.
If Tow/Haul Mode is off and this
setting is on for a Trailer Profile,
each time the ignition is turned on a

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
Vehicle Care 327
Vehicle Care
General Information
General Information . . . . . . . . . . 328
California Proposition65 Warning . . . . . . . . . . . . . . . . . 329
California Perchlorate Materials Requirements . . . . . 329
Accessories and Modifications . . . . . . . . . . . . . . . . 329
Vehicle Checks
Doing Your OwnService Work . . . . . . . . . . . . . . . 330
Hood . . . . . . . . . . . . . . . . . . . . . . . . . 330
Engine Compartment Overview . . . . . . . . . . . . . . . . . . . . 332
Engine Oil . . . . . . . . . . . . . . . . . . . . 339
Engine Oil Life System . . . . . . . 341
Automatic Transmission Fluid . . . . . . . . . . . . . . . . . . . . . . . . 343
Engine Air Filter Life System . . . . . . . . . . . . . . . . . . . . . . 343
Engine Air Cleaner/Filter . . . . . . 344
Cooling System . . . . . . . . . . . . . . 346
Engine Overheating . . . . . . . . . . 351
Overheated Engine Protection Operating Mode . . . . . . . . . . . . . 352
Engine Fan . . . . . . . . . . . . . . . . . . . 353 Power Steering Fluid . . . . . . . . . 354
Washer Fluid . . . . . . . . . . . . . . . . . 354
Brakes . . . . . . . . . . . . . . . . . . . . . . . 355
Brake Pad Life System . . . . . . . 356
Brake Fluid . . . . . . . . . . . . . . . . . . . 357
Battery - North America . . . . . . 358
Four-Wheel Drive . . . . . . . . . . . . . 361
Front Axle . . . . . . . . . . . . . . . . . . . . 361
Rear Axle . . . . . . . . . . . . . . . . . . . . 362
Noise Control System . . . . . . . . 362
Starter Switch Check . . . . . . . . . 363
Automatic Transmission Shift
Lock Control Function
Check . . . . . . . . . . . . . . . . . . . . . . . 363
Ignition Transmission Lock Check . . . . . . . . . . . . . . . . . . . . . . . 363
Park Brake and P (Park) Mechanism Check . . . . . . . . . . 364
Wiper Blade Replacement . . . . 364
Windshield Replacement . . . . . 365
Gas Strut(s) . . . . . . . . . . . . . . . . . . 365
Headlamp Aiming
Headlamp Aiming . . . . . . . . . . . . 366
Bulb Replacement
Bulb Replacement . . . . . . . . . . . . 367
Halogen Bulbs . . . . . . . . . . . . . . . . 367
LED Lighting . . . . . . . . . . . . . . . . . 367 Headlamps, Front Turn Signal,
Sidemarker, and Parking
Lamps . . . . . . . . . . . . . . . . . . . . . . 367
Taillamps, Turn Signal, Stoplamps, and Back-Up
Lamps . . . . . . . . . . . . . . . . . . . . . . 368
Center High-Mounted Stoplamp (CHMSL) and
Cargo Lamp . . . . . . . . . . . . . . . . . 369
License Plate Lamp . . . . . . . . . . 369
Electrical System
Electrical System Overload . . . 370
Fuses and Circuit Breakers . . . 370
Engine Compartment Fuse Block . . . . . . . . . . . . . . . . . . . . . . . . 371
Instrument Panel Fuse
Block (Left) . . . . . . . . . . . . . . . . . 374
Instrument Panel Fuse Block (Right) . . . . . . . . . . . . . . . . . . . . . . 376
Wheels and Tires
Tires . . . . . . . . . . . . . . . . . . . . . . . . . . 379
All-Season Tires . . . . . . . . . . . . . . 379
Winter Tires . . . . . . . . . . . . . . . . . . 380
Low-Profile Tires . . . . . . . . . . . . . 380
All-Terrain Tires . . . . . . . . . . . . . . . 381
Tire Sidewall Labeling . . . . . . . . 381
Tire Designations . . . . . . . . . . . . . 383
Tire Terminology andDefinitions . . . . . . . . . . . . . . . . . . 385

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 4/10/19
Vehicle Care 349
Automatic Coolant Service Fill
Instructions (L3B Engine)
See 3.0L Duramax Diesel
supplement for the diesel engine
procedure.
If equipped, this feature assists in
filling and removing air from the
cooling system after service of
components or when coolant is
added after being too low.
To activate the fill and air removal
process:1. With a cold system, add coolant to the indicated mark
on the surge tank.
2. Replace the cap on the surge tank.
3. Connect the vehicle to a battery charger.
4. Set the ignition to Service or Accessory Mode. See Ignition
Positions (Keyless Access)
0 208 or
Ignition Positions (Key Access)
0 210.
5. Turn off the air conditioning. 6. Set the parking brake.
7. At the same time, press the
accelerator and the brake for
automatic transmission
vehicles for two seconds, then
release.
At the end of the cycle, check the
coolant level in the surge tank and
add coolant if it is low. Turn off the
vehicle, allow the Electronic Control
Module (ECM) to go to sleep, about
two minutes, and repeat Steps 3–7.
Listen for pump activation and
movement of the control valves
while watching the level of the
coolant in the surge tank. If the tank
empties, turn the ignition off,
carefully remove the surge tank cap,
refill to the indicated mark, and
repeat Steps 3–6. The fill and air
removal process will run for
approximately 10 minutes.
How to Add Coolant to the
Coolant Surge Tank for
Gasoline Engines Except L3B
If the vehicle has a diesel engine,
see “Cooling System” in the
Duramax diesel supplement for the
proper coolant fill procedure.
{Warning
Spilling coolant on hot engine
parts can burn you. Coolant
contains ethylene glycol and it will
burn if the engine parts are hot
enough.
{Warning
Plain water, or other liquids such
as alcohol, can boil before the
proper coolant mixture will. With
plain water or the wrong mixture,
the engine could get too hot but
there would not be an overheat
(Continued)