ECU GMC SIERRA DENALI 2020 Repair Manual

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 427
Warning (Continued)
negative battery cable and cover
the negative battery post and
cable with a non-conductive
material. If the battery is left
connected or the battery cable
contacts the post, the Electric
Parking Brake may activate
during towing, which could cause
a crash.
8. Disconnect the negative (–) battery cable. See “Negative
Battery Cable Disconnection”
in Battery - North America
0 358.
9. Shift the transmission to P (Park).
Caution
If the steering column is locked,
vehicle damage may occur. 10. Move the steering wheel to
make sure the steering column
is unlocked.
11. If the vehicle has an ignition key, keep it in the towed
vehicle in ACC/ACCESSORY
to prevent the steering column
from locking. If the vehicle is
equipped with 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. See
Door Locks 026.
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 0358. 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) 0208 or
Ignition Positions (Key Access)
0 210.
4. Set the parking brake. See Electric Parking Brake 0233.
5. Disconnect from the tow vehicle.
6. Shift the transmission to N (Neutral).
7. Shift the transfer case to 2
m
(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
0 141.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
438 Vehicle Care
Floor Mats
{Warning
If a floor mat is the wrong size or
is not properly installed, it can
interfere with the pedals.
Interference with the pedals can
cause unintended acceleration
and/or increased stopping
distance which can cause a crash
and injury. Make sure the floor
mat does not interfere with the
pedals.
Use the following guidelines for
proper floor mat usage:
. The original equipment floor
mats were designed for your
vehicle. If the floor mats need
replacing, it is recommended
that GM certified floor mats be
purchased. Non-GM floor mats
may not fit properly and may
interfere with the pedals. Always
check that the floor mats do not
interfere with the pedals. .
Do not use a floor mat if the
vehicle is not equipped with a
floor mat retainer on the driver
side floor.
. Use the floor mat with the
correct side up. Do not turn
it over.
. Do not place anything on top of
the driver side floor mat.
. Use only a single floor mat on
the driver side.
. Do not place one floor mat on
top of another.
Removing and Replacing the
Floor Mats
Pull up on the rear of the driver side
floor mat to unlock each retainer
and remove.
Reinstall by lining up the floor mat
retainer openings over the carpet
retainers and snapping into position.
Make sure the floor mat is properly
secured in place.
Verify the floor mat does not
interfere with the pedals.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
462 Customer Information
Customer
Information
Customer Information
Customer SatisfactionProcedure . . . . . . . . . . . . . . . . . . . 462
Customer Assistance Offices . . . . . . . . . . . . . . . . . . . . . . 464
Customer Assistance for Text Telephone (TTY) Users . . . . . 465
Online Owner Center . . . . . . . . . 465
GM Mobility Reimbursement Program . . . . . . . . . . . . . . . . . . . . 465
Roadside Assistance Program . . . . . . . . . . . . . . . . . . . . 466
Scheduling Service Appointments . . . . . . . . . . . . . . . 467
Courtesy Transportation Program . . . . . . . . . . . . . . . . . . . . 468
Collision Damage Repair . . . . . 469
Publication Ordering Information . . . . . . . . . . . . . . . . . . 471
Radio Frequency Statement . . . . . . . . . . . . . . . . . . . 472
Reporting Safety Defects
Reporting Safety Defects tothe United States
Government . . . . . . . . . . . . . . . . . 472
Reporting Safety Defects to the Canadian
Government . . . . . . . . . . . . . . . . . 472
Reporting Safety Defects to General Motors . . . . . . . . . . . . . 473
Vehicle Data Recording and
Privacy
Vehicle Data Recording andPrivacy . . . . . . . . . . . . . . . . . . . . . . 473
Cybersecurity . . . . . . . . . . . . . . . . . 474
Event Data Recorders . . . . . . . . 474
OnStar . . . . . . . . . . . . . . . . . . . . . . . 475
Infotainment System . . . . . . . . . . 475
Customer 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

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
466 Customer Information
Center at 1-800-323-9935. Text
Telephone (TTY) users, call
1-800-833-9935.
General Motors of Canada also has
a Mobility program. See www.gm.ca
or call 1-800-GM-DRIVE
(800-463-7483) for details. TTY
users call 1-800-263-3830.
Roadside Assistance
Program
For U.S.-purchased vehicles, call
1-888-881-3302; (Text Telephone
(TTY): 1-888-889-2438).
For Canadian-purchased vehicles,
call 1-800-268-6800.
Service is available 24 hours a day,
365 days a year.
Calling for Assistance
When calling Roadside Assistance,
have the following information
ready:
.Your name, home address, and
home telephone number
. Telephone number of your
location .
Location of the vehicle
. Model, year, color, and license
plate number of the vehicle
. Odometer reading, Vehicle
Identification Number (VIN), and
delivery date of the vehicle
. Description of the problem
Coverage
Services are provided for the
duration of the vehicle's powertrain
warranty.
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

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
474 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 connectyour 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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
476 OnStar
OnStar
OnStar Overview
OnStar Overview . . . . . . . . . . . . . 476
OnStar Services
Emergency . . . . . . . . . . . . . . . . . . . 477
Security . . . . . . . . . . . . . . . . . . . . . . 478
OnStar Additional Information
OnStar AdditionalInformation . . . . . . . . . . . . . . . . . . 478
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. Press
Q
twice 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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
OnStar 477
Press=to:
. Open the OnStar app on the
infotainment display. See the
infotainment manual 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.
. 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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
478 OnStar
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.
Press
Qto 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.
Reactivation for Subsequent
Owners
PressQand follow the prompts to
speak to an Advisor as soon as
possible. The Advisor will update
vehicle records and explain OnStar
or connected service options.
How OnStar Service Works
Automatic Crash Response,
Emergency Services, Crisis Assist,
Stolen Vehicle Assistance, Remote
Services, and Roadside Assistance
are available on most vehicles. Not
all OnStar services are available
everywhere or on all vehicles. For
more information, a full description
of OnStar services, system
limitations, and OnStar User Terms,
Privacy Statement, and Software
Terms:
. Call 1-888-4ONSTAR
(1-888-466-7827).
. See www.onstar.com (U.S.).
. See www.onstar.ca (Canada).
. Call TTY 1-877-248-2080.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
OnStar 481
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, identify whether
updates or changes are available,
or deliver updates or changes. An
active OnStar agreement constitutes
consent to these software updates
or changes and agreement that
either OnStar or GM may remotely
deliver them to the vehicle.Privacy
The complete OnStar Privacy
Statement may be found at
www.onstar.com (U.S.),
or www.onstar.ca (Canada). We
recommend that you review it. If you
have any questions, call
1-888-4ONSTAR (1-888-466-7827)
or press
Qto speak with an
Advisor. Users of wireless
communications are cautioned that
the privacy of any information sent
via wireless cellular communications
cannot be assured. Third parties
may unlawfully intercept or access
transmissions and private
communications without consent.
OnStar - Software
Acknowledgements
Certain OnStar components include
libcurl and unzip software and other
third party software. Below are the
notices and licenses associated with
libcurl and unzip and for other third
party software please see http://
opensource.lge.com/index
www.onstar.com/us/en/ libcurl:
COPYRIGHT AND PERMISSION
NOTICE
Copyright (c) 1996 - 2010, Daniel
Stenberg, .
All rights reserved.
Permission to use, copy, modify,
and distribute this software for any
purpose with or without fee is
hereby granted, provided that the
above copyright notice and this
permission notice appear in all
copies.
THE SOFTWARE IS PROVIDED
“AS IS,”
WITHOUT WARRANTY OF
ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT
LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE
AND NONINFRINGEMENT OF
THIRD PARTY RIGHTS. IN NO
EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM,
DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF
CONTRACT, TORT OR

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
482 OnStar
OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE
USE OR OTHER DEALINGS IN
THE SOFTWARE.
Except as contained in this notice,
the name of a copyright holder shall
not be used in advertising or
otherwise to promote the sale, use
or other dealings in this Software
without prior written authorization of
the copyright holder.
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