2021 GMC SIERRA ECU

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
Vehicle Care 397
Keyless Access, keep the RKE transmitter
outside of the vehicle and manually lock
the doors. Access the vehicle by using
the key in the door lock. SeeDoor Locks
0 21.
Disconnecting the Towed Vehicle
Before disconnecting from the tow vehicle: 1. Park on a level surface. Secure the vehicle with wheel blocks.
2. Re-connect the negative (–) battery. See Battery - North America 0343.
3. Turn on the ignition with the engine off. For vehicles with a key, turn the ignition
to ON/RUN with the engine off. If the
vehicle is equipped with Keyless Access,
with your foot off the brake pedal, press
and hold ENGINE START/STOP for
five seconds until the green light comes
on in the button. See Ignition Positions
(Keyless Access) 0230 or
Ignition Positions (Key Access) 0229.
4. Set the parking brake. See Electric
Parking Brake 0247.
5. Disconnect from the tow vehicle.
6. Shift the transmission to N (Neutral). 7. Shift the transfer case to 2m(Two-Wheel
Drive High). When the shift to 2
m
(Two-Wheel Drive High) is complete, the
light in the instrument cluster will stop
flashing and stay lit. See
Four-Wheel-Drive Light 0118.
8. Start the engine. Check that the vehicle is in 2
m(Two-Wheel Drive High) by
starting the engine and shifting the
transmission to D (Drive) and then to
R (Reverse). There should be movement
of the vehicle while shifting.
9. Shift the transmission to P (Park) and turn off the ignition.
10. Release the parking brake and remove the wheel blocks.
11. Reset any lost presets. The outside temperature display will
default to 0 °C (32 °F) but will reset with
normal usage.
Dolly Towing

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
406 Vehicle Care
Use the following guidelines for proper floor
mat/liner usage:
.The original equipment floor mats/liners
were designed for your vehicle. If the
floor mats/liners need replacing, it is
recommended that GM certified floor
mats/liners be purchased. Non-GM floor
mats/liners may not fit properly and may
interfere with the pedals. Always check
that the floor mat, liner, or liner insert
does not interfere with the pedals.
.Do not use a floor mat/liner if the vehicle
is not equipped with a floor mat retainer
on the driver side floor.
.Use the floor mat/liner insert with the
correct side up. Do not turn it over.
.Do not place anything on top of the
driver side floor mat/liner.
.Use only a single floor mat/liner on the
driver side.
.Do not place one floor mat/liner on top
of another.
Removing and Replacing the Floor Mats/
Liners
Pull up on the rear of the driver side floor
mat/liner to unlock each retainer and
remove.
Reinstall by lining up the floor mat/liner
retainer openings over the carpet retainers
and snapping into position.
Make sure the floor mat/liner is properly
secured in place.
Verify the floor mat/liner does not interfere
with the pedals.
Removing and Replacing the Floor Liner
Inserts
Pull up on the edge of the driver side floor
liner insert to unlock each button clip and
remove.
Reinstall by lining up the floor liner insert
button clips over the liner retainers and
snapping into position.
Make sure the floor liner insert is properly
secure in place using all button clips.
Verify the floor liner insert does not
interfere with the pedals.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
428 Customer Information
Customer Information
Customer Information
Customer Satisfaction Procedure . . . . . . 428
Customer Assistance Offices . . . . . . . . . . . 430
Customer Assistance for Text Telephone(TTY) Users . . . . . . . . . . . . . . . . . . . . . . . . . . 430
Online Owner Center . . . . . . . . . . . . . . . . . . 430
GM Mobility Reimbursement Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 431
Roadside Assistance Program . . . . . . . . . . 431
Scheduling Service Appointments . . . . . . 433
Courtesy Transportation Program . . . . . 433
Collision Damage Repair . . . . . . . . . . . . . . . 434
Publication Ordering Information . . . . . . 435
Radio Frequency Statement . . . . . . . . . . . 436
Reporting Safety Defects
Reporting Safety Defects to the United States Government . . . . . . . . . . . . . . . . . . 436
Reporting Safety Defects to the Canadian Government . . . . . . . . . . . . . . . 437
Reporting Safety Defects to General Motors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437
Vehicle Data Recording and Privacy
Vehicle Data Recording and Privacy . . . 437
Cybersecurity . . . . . . . . . . . . . . . . . . . . . . . . . 438
Event Data Recorders . . . . . . . . . . . . . . . . . . 438
OnStar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
Infotainment System . . . . . . . . . . . . . . . . . . 439Customer Information
Customer Satisfaction Procedure
Your satisfaction and goodwill are important
to your dealer and to GMC. Normally, any
concerns with the sales transaction or the
operation of the vehicle will be resolved by
your dealer's sales or service departments.
Sometimes, however, despite the best
intentions of all concerned,
misunderstandings can occur. If your concern
has not been resolved to your satisfaction,
the following steps should be taken:
STEP ONE : Discuss your concern with a
member of dealership management.
Normally, concerns can be quickly resolved
at that level. If the matter has already been
reviewed with the sales, service, or parts
manager, contact the owner of your
dealership or the general manager.
STEP TWO : If after contacting a member of
dealership management, it appears your
concern cannot be resolved by your
dealership without further help, in the U.S.,
call 1-800-462-8782. In Canada, call General
Motors of Canada Customer Care Centre at
1-800-263-3777 (English), or 1-800-263-7854
(French).

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
432 Customer Information
In the U.S., anyone driving the vehicle is
covered. In Canada, a person driving the
vehicle without permission from the owner
is not covered.
Roadside Assistance is not a part of the New
Vehicle Limited Warranty. General Motors
North America and GMC reserve the right to
make any changes or discontinue the
Roadside Assistance program at any time
without notification.
General Motors North America and GMC
reserve the right to limit services or
payment to an owner or driver if they
decide the claims are made too often, or the
same type of claim is made many times.
Services Provided
.Emergency Fuel Delivery:Delivery of
enough fuel for the vehicle to get to the
nearest service station.
.Lock-Out Service: Service to unlock the
vehicle if you are locked out. A remote
unlock may be available if you have
OnStar. For security reasons, the driver
must present identification before this
service is given.
.Emergency Tow from a Public Road or
Highway: Tow to the nearest GMC dealer
for warranty service, or if the vehicle was in a crash and cannot be driven.
Assistance is not given when the vehicle
is stuck in the sand, mud, or snow.
.Flat Tire Change:
Service to change a flat
tire with the spare tire. The spare tire,
if equipped, must be in good condition
and properly inflated. It is the owner's
responsibility for the repair or
replacement of the tire if it is not covered
by the warranty.
.Battery Jump Start: Service to jump start
a dead battery.
.Trip Interruption Benefits and Assistance:
If your trip is interrupted due to a
warranty event, incidental expenses may
be reimbursed within the Powertrain
warranty period. Items considered are
reasonable and customary hotel, meals,
rental car, or a vehicle being delivered
back to the customer, up to 500 miles.
Services Not Included in Roadside
Assistance
.Impound towing caused by violation of
any laws
.Legal fines
.Mounting, dismounting, or changing of
snow tires, chains, or other traction
devices Service is not provided if a vehicle is in an
area that is not accessible to the service
vehicle or is not a regularly traveled or
maintained public road, which includes ice
and winter roads. Off-road use is not
covered.
Services Specific to Canadian-Purchased
Vehicles
.Fuel Delivery:
Reimbursement is up to 7 L.
Diesel fuel delivery may be restricted.
Propane and other fuels are not provided
through this service.
.Lock-Out Service: Vehicle registration is
required.
.Trip Interruption Benefits and Assistance:
Must be over 150 km from where your
trip was started to qualify.
Pre-authorization, original detailed
receipts, and a copy of the repair orders
are required. Once authorization has been
received, the Roadside Assistance advisor
will help to make arrangements and
explain how to receive payment.
.Alternative Service: If assistance cannot
be provided right away, the Roadside
Assistance advisor may give permission to
get local emergency road service. You will
receive payment, up to $100, after
sending the original receipt to Roadside

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
438 Customer Information
Cybersecurity
GM collects information about the use of
your vehicle including operational and safety
related information. We collect this
information to provide, evaluate, improve,
and troubleshoot our products and services
and to develop new products and services.
The protection of vehicle electronics systems
and customer data from unauthorized
outside electronic access or control is
important to GM. GM maintains appropriate
security standards, practices, guidelines and
controls aimed at defending the vehicle and
the vehicle service ecosystem against
unauthorized electronic access, detecting
possible malicious activity in related
networks, and responding to suspected
cybersecurity incidents in a timely,
coordinated and effective manner. Security
incidents could impact your safety or
compromise your private data. To minimize
security risks, please do not connect your
vehicle electronic systems to unauthorized
devices or connect your vehicle to any
unknown or untrusted networks (such as
Bluetooth, WIFI or similar technology). In
the event you suspect any security incident
impacting your data or the safe operation of
your vehicle, please stop operating your
vehicle and contact your dealer.
Event Data Recorders
This vehicle is equipped with an event data
recorder (EDR). The main purpose of an EDR
is to record, in certain crash or near
crash-like situations, such as an air bag
deployment or hitting a road obstacle, data
that will assist in understanding how a
vehicle’s systems performed. The EDR is
designed to record data related to vehicle
dynamics and safety systems for a short
period of time, typically 30 seconds or less.
The EDR in this vehicle is designed to record
such data as:
.How various systems in your vehicle were
operating;
.Whether or not the driver and passenger
safety belts were buckled/fastened;
.How far (if at all) the driver was
depressing the accelerator and/or brake
pedal; and,
.How fast the vehicle was traveling.
These data can help provide a better
understanding of the circumstances in which
crashes and injuries occur.
Note
EDR data are recorded by your vehicle only
if a non-trivial crash situation occurs; no
data are recorded by the EDR under normal driving conditions and no personal data
(e.g., name, gender, age, and crash location)
are recorded. However, other parties, such
as law enforcement, could combine the EDR
data with the type of personally identifying
data routinely acquired during a crash
investigation.
To read data recorded by an EDR, special
equipment is required, and access to the
vehicle or the EDR is needed. In addition to
the vehicle manufacturer, other parties, such
as law enforcement, that have the special
equipment, can read the information if they
have access to the vehicle or the EDR.
GM will not access these data or share it
with others except: with the consent of the
vehicle owner or, if the vehicle is leased,
with the consent of the lessee; in response
to an official request by police or similar
government office; as part of GM's defense
of litigation through the discovery process;
or, as required by law. Data that GM collects
or receives may also be used for GM
research needs or may be made available to
others for research purposes, where a need
is shown and the data is not tied to a
specific vehicle or vehicle owner.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
440 OnStar
OnStar
OnStar Overview
OnStar Overview . . . . . . . . . . . . . . . . . . . . . . 440
OnStar Services
Emergency . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
OnStar Additional Information
OnStar Additional Information . . . . . . . . . 441
OnStar Overview
=Voice Command Button
QBlue OnStar Button
>Red Emergency Button
This vehicle may be equipped with a
comprehensive, in-vehicle system that can
connect to an OnStar Advisor for Emergency,
Security, Navigation, Connections, and
Diagnostics Services. OnStar services may
require a paid service plan and data plan.
OnStar requires the vehicle battery and
electrical system, cellular service, and GPS
satellite signals to be available and
operating. OnStar acts as a link to existing
emergency service providers. OnStar may
collect information about you and your
vehicle, including location information. See
OnStar User Terms, Privacy Statement, and
Software Terms for more details including
system limitations at www.onstar.com (U.S.)
or www.onstar.ca (Canada). The OnStar system status light is next to
the OnStar buttons. If the status light is:
.Solid Green: System is ready.
.Flashing Green: On a call.
.Red: Indicates a problem.
.Off: System is off. PressQtwice to
speak with an OnStar Advisor.
Press
Qor call 1-888-4ONSTAR
(1-888-466-7827) to speak to an Advisor.
Functionality of the Voice Command button
may vary by vehicle and region.
Press
=to:
.Open the OnStar app on the infotainment
display. See OnStar System 0162 for
information on how to use the
OnStar app.
Or
.Give OnStar Turn-by-Turn Navigation voice
commands.
.Obtain and customize the Wi-Fi hotspot
name or SSID and password, if equipped.
Press
Qto connect to an Advisor to:
.Verify account information or update
contact information.
.Get driving directions.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
OnStar 441
.Receive a Diagnostic check of the vehicle's
key operating systems.
.Receive Roadside Assistance.
.Manage Wi-Fi Settings, if equipped.
Press
>to get a priority connection to an
OnStar Advisor available 24/7 to:
.Get help for an emergency.
.Be a Good Samaritan or respond to an
AMBER Alert.
.Get assistance in severe weather or other
crisis situations and find evacuation
routes.
OnStar Services
Emergency
Emergency Services require an active safety
and security plan. With Automatic Crash
Response, built-in sensors can automatically
alert a specially trained OnStar Advisor who
is immediately connected in to the vehicle
to help.
Press
>for a priority connection to an
OnStar Advisor who can contact emergency
service providers, direct them to your exact
location, and relay important information. With OnStar Crisis Assist, specially trained
Advisors are available 24 hours a day, 7 days
a week, to provide a central point of
contact, assistance, and information during a
crisis.
With Roadside Assistance, Advisors can
locate a nearby service provider to help with
a flat tire, a battery jump, or an empty
gas tank.
Security
If equipped, OnStar provides these services:
.With Stolen Vehicle Assistance, OnStar
Advisors can use GPS to pinpoint the
vehicle and help authorities quickly
recover it.
.With Remote Ignition Block, if equipped,
OnStar can block the engine from being
restarted.
.With Stolen Vehicle Slowdown,
if equipped, OnStar can work with law
enforcement to gradually slow the
vehicle down.
Theft Alarm Notification
If equipped, if the doors are locked and the
vehicle alarm sounds, a notification by text,
e-mail, or phone call will be sent. If the
vehicle is stolen, an OnStar Advisor can work
with authorities to recover the vehicle.
OnStar Additional
Information
In-Vehicle Audio Messages
Audio messages may play important
information at the following times:
.Prior to vehicle purchase. PressQto set
up an account.
.After change in ownership and at
90 days.
Transferring Service
PressQto request account transfer
eligibility information. The Advisor can
cancel or change account information.
Selling/Transferring the Vehicle
Call 1-888-4ONSTAR (1-888-466-7827)
immediately to terminate your OnStar or
connected services if the vehicle is disposed
of, sold, transferred, or if the lease ends.

GMC Sierra/Sierra Denali 1500 Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-14632426) - 2021 - CRC - 11/5/20
OnStar 443
Languages
The vehicle can be programmed to respond
in multiple languages. Press
Qand ask for
an Advisor. Advisors are available in English,
Spanish, and French. Available languages
may vary by country.
Potential Issues
OnStar cannot perform Remote Door Unlock
or Stolen Vehicle Assistance after the vehicle
has been off continuously for 10 days
without an ignition cycle. If the vehicle has
not been started for 10 days, OnStar can
contact Roadside Assistance or a locksmith
to help gain access to the vehicle.
Global Positioning System (GPS)
.Obstruction of the GPS can occur in a
large city with tall buildings; in parking
garages; around airports; in tunnels and
underpasses; or in an area with very
dense trees. If GPS signals are not
available, the OnStar system should still
operate to call OnStar. However, OnStar
could have difficulty identifying the exact
location.
.In emergency situations, OnStar can use
the last stored GPS location to send to
emergency responders. A temporary loss of GPS can cause loss of
the ability to send a Turn-by-Turn
Navigation route. The Advisor may give a
verbal route or may ask for a call back after
the vehicle is driven into an open area.
Cellular and GPS Antennas
Cellular reception is required for OnStar to
send remote signals to the vehicle. Do not
place items over or near the antenna to
prevent blocking cellular and GPS signal
reception.
Unable to Connect to OnStar Message
If there is limited cellular coverage or the
cellular network has reached maximum
capacity, this message may come on. Press
Qto try the call again or try again after
driving a few miles into another
cellular area.
Vehicle and Power Issues
OnStar services require a vehicle electrical
system, wireless service, and GPS satellite
technologies to be available and operating
for features to function properly. These
systems may not operate if the battery is
discharged or disconnected.
Add-on Electrical Equipment
The OnStar system is integrated into the
electrical architecture of the vehicle. Do not
add any electrical equipment. See Add-On
Electrical Equipment 0318. Added electrical
equipment may interfere with the operation
of the OnStar system and cause it to not
operate.
Vehicle Software Updates
OnStar or GM may remotely deliver
software updates or changes to the vehicle
without further notice or consent. These
updates or changes may enhance or
maintain safety, security, or the operation
of the vehicle or the vehicle systems.
Software updates or changes may affect or
erase data or settings that are stored in the
vehicle, such as saved navigation
destinations or pre-set radio stations.
Neither OnStar nor GM is responsible for
any affected or erased data or settings.
These updates or changes may also collect
personal information. Such collection is
described in the OnStar privacy statement or
separately disclosed at the time of
installation. These updates or changes may
also cause a system to automatically
communicate with GM servers to collect
information about vehicle system status,