2024 GMC SIERRA ECU

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/7/22
32 Keys, Doors, and Windows
Keep hands, children, pets, objects, and
clothing clear of the power assist steps
when in motion. The steps will reverse
direction if they encounter an obstruction
when opening or closing. Remove the
obstruction, then open and close the door
on the same side to complete the motion of
the assist steps. If the obstruction is not
cleared, the assist steps remain extended
while driving.
Extend or retract both power assist steps
for cleaning through the vehicle settings
menu. To view available settings from the
infotainment screen, touch Settings >
Vehicle > Comfort and Convenience.
Enable/Disable
The power assist steps can be enabled or
disabled through the vehicle settings menu.
To view available settings from the
infotainment screen, touch Settings >
Vehicle > Comfort and Convenience.
Vehicle Security
This vehicle has theft-deterrent features;
however, they do not make the vehicle
impossible to steal.
Vehicle Alarm System
The indicator light, on the instrument panel
near the windshield, indicates the status of
the system.
Off :Alarm system is disarmed.
On Solid : Vehicle is secured during the
delay to arm the system.
Fast Flash : Vehicle is unsecured. A door or
the hood is open.
Slow Flash : Alarm system is armed.
Arming the Alarm System
1. Turn off the vehicle. 2. Lock the vehicle in one of two ways:
.Use the remote key.
.With a door open, pressQon the
interior of the door.
3. After 30 seconds, the alarm system will arm and the indicator light will begin to
slowly flash. Pressing
Qon the remote
key a second time will bypass the
30-second delay and immediately arm
the alarm system.
The vehicle alarm system will not arm if the
doors are locked with the key.
If the driver door is opened without first
unlocking with the remote key, the horn will
chirp and the lights will flash to indicate
pre-alarm. If the vehicle is not started,
or the door is not unlocked by pressing
K
on the remote key during the 10-second
pre-alarm, the alarm will be activated.
The alarm will also be activated if a
passenger door or the hood is opened
without first disarming the system. When
the alarm is activated, the turn signals flash
and the horn sounds for about 30 seconds.
The alarm system will then re-arm to
monitor for the next unauthorized event.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/7/22
34 Keys, Doors, and Windows
The security light, in the instrument cluster,
comes on if there is a problem with arming
or disarming the theft-deterrent system.
The system has one or more remote keys
matched to an immobilizer control unit in
your vehicle. Only a correctly matched
remote key will start the vehicle. If the
remote key is ever damaged, you may not
be able to start your vehicle.
When trying to start the vehicle, the
security light may come on briefly when the
ignition is turned on. If the engine does not
start and the security light stays on, there is
a problem with the system. Turn the
ignition off and try again.
If the vehicle will not change ignition modes
(accessory mode, on, off), and the remote
key appears to be undamaged, try another
remote key. Or, you may try placing the
remote key in the remote key pocket
located in the center console. SeeRemote
Key Operation 015.
If the ignition mode will not change with
the other remote key or with the remote
key in the remote key pocket, your vehicle
needs service. If the ignition does change
modes, the first remote key may be faulty. See your dealer who can service the
theft-deterrent system and have a new
remote key programmed to the vehicle.
It is possible for the immobilizer system to
learn new or replacement remote keys. Up
to eight remote keys can be programmed
for the vehicle. To program additional
remote keys, see "Programming Remote
Keys to the Vehicle" under
Remote Key
Operation 015.
Do not leave the remote key or device that
disarms or deactivates the vehicle theft
system in the vehicle.
Exterior Mirrors
Convex Mirrors
{Warning
A convex mirror can make things, like
other vehicles, look farther away than
they really are. If you cut too sharply
into the right lane, you could hit a
vehicle on the right. Check the inside
mirror or glance over your shoulder
before changing lanes. Standard Mirrors
If equipped, the passenger side mirror is
convex shaped. A convex mirror surface is
curved so more can be seen from the
driver seat.
Trailer-Tow Mirrors
The upper portion of both the driver and
passenger mirrors is flat.
The lower portion of both the driver and
passenger mirrors is convex. A convex mirror
surface is curved so more can be seen from
the driver seat. The lower portion is
adjusted manually.
Manual Mirrors
If equipped, adjust manual mirrors by
moving the mirror up and down or left to
right to see a little of the side of the vehicle
and to have a clear view behind the vehicle.
Using hood-mounted air deflectors and
add-on convex mirror attachments could
decrease mirror performance.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/7/22
46 Seats and Restraints
Seats and Restraints
Head Restraints
Head Restraints . . . . . . . . . . . . . . . . . . . . . . . . 47
Front Seats
Seat Adjustment . . . . . . . . . . . . . . . . . . . . . . . 48
Center Seat . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Power Seat Adjustment . . . . . . . . . . . . . . . . 49
Reclining Seatbacks . . . . . . . . . . . . . . . . . . . . . 49
Lumbar Adjustment . . . . . . . . . . . . . . . . . . . . 50
Massage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Memory Seats . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Heated and Ventilated Front Seats . . . . . 54
Rear Seats
Rear Seats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Heated Rear Seats . . . . . . . . . . . . . . . . . . . . . . 56
Seat Belts
Seat Belts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Buckle To Drive . . . . . . . . . . . . . . . . . . . . . . . . . 58
How to Wear Seat Belts Properly . . . . . . 58
Lap-Shoulder Belt . . . . . . . . . . . . . . . . . . . . . . 60
Seat Belt Use During Pregnancy . . . . . . . . 63
Seat Belt Extender . . . . . . . . . . . . . . . . . . . . . . 63
Safety System Check . . . . . . . . . . . . . . . . . . . 63
Seat Belt Care . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Replacing Seat Belt System Parts after aCrash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Airbag System
Airbag System . . . . . . . . . . . . . . . . . . . . . . . . . 64
Where Are the Airbags? . . . . . . . . . . . . . . . . 66
When Should an Airbag Inflate? . . . . . . . . 67
What Makes an Airbag Inflate? . . . . . . . . 68
How Does an Airbag Restrain? . . . . . . . . . 68
What Will You See after an AirbagInflates? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Passenger Sensing System . . . . . . . . . . . . . 69
Servicing the Airbag-Equipped Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Adding Equipment to the Airbag-Equipped Vehicle . . . . . . . . . . . . . . 73
Airbag System Check . . . . . . . . . . . . . . . . . . . 74
Replacing Airbag System Parts after a Crash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Child Restraints
Older Children . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Infants and Young Children . . . . . . . . . . . . . 76
Child Restraint Systems . . . . . . . . . . . . . . . . 78
Where to Put the Restraint . . . . . . . . . . . . 80
Lower Anchors and Tethers for Children(LATCH System) . . . . . . . . . . . . . . . . . . . . . . . 81
Replacing LATCH System Parts After a Crash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Securing Child Restraints (With the Seat Belt in the Center Front Seat) . . . . . . . . 92
Securing Child Restraints (With the Seat Belt in the Rear Seat) . . . . . . . . . . . . . . . . . 92 Securing Child Restraints (With the Seat
Belt in the Front Passenger Seat) . . . . . 95

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/7/22
Seats and Restraints 61
2. Pick up the latch plate and pull the beltacross you. Do not let it get twisted.
The lap-shoulder belt may lock if you
pull the belt across you very quickly.
If this happens, let the belt go back
slightly to unlock it. Then pull the belt
across you more slowly.
If the shoulder portion of a passenger
belt is pulled out all the way, the child
restraint locking feature may be
engaged. See Child Restraint Systems
0 78. If this occurs, let the belt go back
all the way and start again. If the
locking feature stays engaged after
letting the belt go back to stowed position on the seat, move the seat
rearward or recline the seat until the
shoulder belt retractor lock releases.
Engaging the child restraint locking
feature in the front outboard seating
position may affect the passenger
sensing system, if equipped. See
Passenger Sensing System
069.
If the webbing locks in the latch plate
before it reaches the buckle, tilt the latch
plate flat to unlock.
3. Push the latch plate into the buckle until
it clicks.
Pull up on the latch plate to make sure
it is secure. If the belt is not long
enough, see Seat Belt Extender 063.
Position the release pushbutton on the
buckle so that the seat belt could be
quickly unbuckled if necessary.
If equipped with a shoulder belt height
adjuster, move it to the height that is
right for you. See "Shoulder Belt Height
Adjuster" later in this section for
instructions on use and important safety
information.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/7/22
Seats and Restraints 63
met. Seat belt pretensioners can also help
tighten the seat belts in a side crash or
rollover event.
Pretensioners work only once. If the
pretensioners activate in a crash, the
pretensioners and probably other parts of
the vehicle seat belt system will need to be
replaced. SeeReplacing Seat Belt System
Parts after a Crash 064.
Do not sit on the outboard seat belt while
entering or exiting the vehicle or at any
time while sitting in the seat. Sitting on the
seat belt can damage the webbing and
hardware.
Rear Seat Belt Comfort Guides
Rear seat belt comfort guides may provide
added seat belt comfort for older children
who have outgrown booster seats and for
some adults. When installed on a shoulder
belt, the comfort guide positions the
shoulder belt away from the neck and head.
Comfort guides are available through your
dealer for the rear outboard seating
positions. Instructions are included with the
comfort guides.
Seat Belt Use During Pregnancy
Seat belts work for everyone, including
pregnant women. Like all occupants, they
are more likely to be seriously injured if
they do not wear seat belts.
A pregnant woman should wear a
lap-shoulder belt, and the lap portion should
be worn as low as possible, below the
rounding, throughout the pregnancy.
The best way to protect the fetus is to
protect the mother. When a seat belt is
worn properly, it is more likely that the
fetus will not be hurt in a crash. For
pregnant women, as for anyone, the key to
making seat belts effective is wearing them
properly.
Seat Belt Extender
If the vehicle seat belt will fasten around
you, you should use it.
But if a seat belt is not long enough, your
dealer will order you an extender. Only a
GM dealer issued extender should be used.
When you go in to order it, take the
heaviest coat you will wear, so the extender
will be long enough for you. To help avoid
personal injury, do not let someone else use
it, and use it only for the seat it is made to
fit. The extender has been designed for
adults. Never use it for securing child
restraints. For more information on the
proper use and fit of seat belt extenders see
the instruction sheet that comes with the
extender.
Safety System Check
Periodically check the seat belt reminder,
seat belts, buckles, latch plates, retractors,
shoulder belt height adjusters (if equipped),
and seat belt anchorages to make sure they
are all in working order. Look for any other
loose or damaged seat belt system parts
that might keep a seat belt system from
performing properly. See your dealer to
have it repaired. Torn, frayed, or twisted
seat belts may not protect you in a crash.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/7/22
Seats and Restraints 65
.A roof-rail airbag for the front outboard
passenger and the passenger seated
directly behind the front outboard
passenger
All vehicle airbags have the word AIRBAG on
the trim or on a label near the deployment
opening.
For frontal airbags, the word AIRBAG is on
the center of the steering wheel for the
driver and on the instrument panel for the
front outboard passenger.
For seat-mounted side impact airbags, the
word AIRBAG is on the side of the seatback
or side of the seat closest to the door.
For roof-rail airbags, the word AIRBAG is on
the ceiling or trim.
Airbags are designed to supplement the
protection provided by seat belts. Even
though today's airbags are also designed to
help reduce the risk of injury from the force
of an inflating bag, all airbags must inflate
very quickly to do their job.
Here are the most important things to know
about the airbag system:{Warning
You can be severely injured or killed in a
crash if you are not wearing your seat
belt, even with airbags. Airbags are
designed to work with seat belts, not
replace them. Also, airbags are not
designed to inflate in every crash. In
some crashes seat belts are the only
restraint. See When Should an Airbag
Inflate? 067.
Wearing your seat belt during a crash
helps reduce your chance of hitting
things inside the vehicle or being ejected
from it. Airbags are “supplemental
restraints” to the seat belts. Everyone in
the vehicle should wear a seat belt
properly, whether or not there is an
airbag for that person.
{Warning
Because airbags inflate with great force
and faster than the blink of an eye,
anyone who is up against, or very close
to, any airbag when it inflates can be
seriously injured or killed. Do not sit
(Continued)
Warning (Continued)
unnecessarily close to any airbag, as you
would be if sitting on the edge of the
seat or leaning forward. Seat belts help
keep you in position before and during a
crash. Always wear a seat belt, even with
airbags. The driver should sit as far back
as possible while still maintaining control
of the vehicle. The seat belts and the
front outboard passenger airbags are
most effective when you are sitting well
back and upright in the seat with both
feet on the floor.
Occupants should not lean on or sleep
against the door or side windows in
seating positions with seat-mounted side
impact airbags and/or roof-rail airbags.
{Warning
Children who are up against, or very
close to, any airbag when it inflates can
be seriously injured or killed. Always
secure children properly in the vehicle. To
read how, seeOlder Children 075 or
Infants and Young Children 076.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/7/22
Seats and Restraints 67
Driver Side Crew Cab Shown, Passenger SideDouble and Regular Cabs Similar
The roof-rail airbags for the driver, front
outboard passenger, and second row
outboard passengers are in the ceiling above
the side windows.
{Warning
If something is between an occupant and
an airbag, the airbag might not inflate
properly or it might force the object into
that person causing severe injury or even
death. The path of an inflating airbag
must be kept clear. Do not put anything
between an occupant and an airbag, and (Continued)
Warning (Continued)
do not attach or put anything on the
steering wheel hub or on or near any
other airbag covering.
Do not use seat accessories that block the
inflation path of a seat-mounted side
impact airbag.
Never secure anything to the roof of a
vehicle with roof-rail airbags by routing a
rope or tie‐down through any door or
window opening. If you do, the path of
an inflating roof-rail airbag will be
blocked.
When Should an Airbag Inflate?
This vehicle is equipped with airbags. See
Airbag System064. Airbags are designed to
inflate if the impact exceeds the specific
airbag system's deployment threshold.
Deployment thresholds are used to predict
how severe a crash is likely to be in time
for the airbags to inflate and help restrain
the occupants. The vehicle has electronic
sensors that help the airbag system
determine the severity of the impact.
Deployment thresholds can vary with
specific vehicle design. Frontal airbags are designed to inflate in
moderate to severe frontal crashes to help
reduce the potential for severe injuries,
mainly to the driver's or front outboard
passenger's head and chest.
Whether the frontal airbags will or should
inflate is not based primarily on how fast
the vehicle is traveling. It depends on what
is hit, the direction of the impact, and how
quickly the vehicle slows down.
Frontal airbags may inflate at different crash
speeds depending on whether the vehicle
hits an object straight on or at an angle,
and whether the object is fixed or moving,
rigid or deformable, narrow or wide.
Frontal airbags are not intended to inflate
during vehicle rollovers, rear impacts,
or many side impacts.
In addition, the vehicle has advanced
technology frontal airbags. Advanced
technology frontal airbags adjust the
restraint according to either crash severity
or occupant interaction.
Seat-mounted side impact airbags are
designed to inflate in moderate to severe
side crashes depending on the location of
the impact. These airbags may also inflate
in some moderate to severe frontal impacts.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/7/22
70 Seats and Restraints
Canada
The words ON and OFF, or the symbols for
on and off, will be visible during the system
check. When the system check is complete,
either the word ON or OFF, or the symbol
for on or off, will be visible. See Passenger
Airbag Status Indicator 0121.
The passenger sensing system turns off the
front outboard passenger frontal airbag
under certain conditions. No other airbag is
affected by the passenger sensing system.
The passenger sensing system works with
sensors that are part of the front outboard
passenger seat and seat belt. The sensors
are designed to detect the presence of a
properly seated occupant and determine if
the front outboard passenger frontal airbag
should be allowed to inflate or not.
According to accident statistics, children are
safer when properly secured in a rear seat
in the correct child restraint for their weight
and size. Whenever possible, children aged 12 and
under should be secured in a rear seating
position.
Never put a rear-facing child seat in the
front. This is because the risk to the
rear-facing child is so great, if the airbag
inflates.
{Warning
A child in a rear-facing child restraint can
be seriously injured or killed if the
passenger frontal airbag inflates. This is
because the back of the rear-facing child
restraint would be very close to the
inflating airbag. A child in a
forward-facing child restraint can be
seriously injured or killed if the passenger
frontal airbag inflates and the passenger
seat is in a forward position.
Even if the passenger sensing system has
turned off the passenger frontal airbag,
no system is fail-safe. No one can
guarantee that an airbag will not deploy
under some unusual circumstance, even
though the airbag is turned off.
(Continued)
Warning (Continued)
Never put a rear-facing child restraint in
the front seat, even if the airbag is off.
If securing a forward-facing child restraint
in the front outboard passenger seat,
always move the seat as far back as it
will go. It is better to secure child
restraints in the rear seat. Consider using
another vehicle to transport the child
when a rear seat is not available.
If the vehicle does not have a rear seat that
will accommodate a rear-facing child
restraint, a rear-facing child restraint should
not be installed in the vehicle, even if the
airbag is off.
The passenger sensing system is designed to
turn off the front outboard passenger
frontal airbag if:
.The front outboard passenger seat is
unoccupied.
.The system determines an infant is
present in a child restraint.
.A front outboard passenger takes his/her
weight off of the seat for a period
of time.