2024 GMC SIERRA ECU

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 213
Using heavier suspension components
to get added durability might not
change the weight ratings. Ask your
dealer to help load the vehicle the
right way.
{Warning
Things you put inside the vehicle can
strike and injure people in a sudden
stop or turn, or in a crash.
.Put things in the cargo area of the
vehicle. Try to spread the weight
evenly.
.Never stack heavier things, like
suitcases, inside the vehicle so
that some of them are above the
tops of the seats.
.Do not leave an unsecured child
restraint in the vehicle.
.When you carry something inside
the vehicle, secure it whenever
you can.
.Do not leave a seat folded down
unless you need to. There is also important loading
information for off-road driving in this
manual. See
“Loading the Vehicle for
Off-Road Driving“ underOff-Road
Driving 0203.
Two-Tiered Loading
Depending on the model of the pickup,
an upper load platform can be created
by positioning three or four 5 cm (2 in)
by 15 cm (6 in) wooden planks across
the width of the pickup box. The planks
must be inserted in the pickup box
depressions.
When using this upper load platform,
be sure the load is securely tied down
to prevent it from shifting. The load's
center of gravity should be positioned
in a zone over the rear axle. The zone is
located in the area between the front
of each wheel well and the rear of each
wheel well. The center of gravity height
must not extend above the top of the
pickup box flareboard. Any load that extends beyond the
vehicle's taillamp area must be properly
marked according to local laws and
regulations.
Remember not to exceed the Gross Axle
Weight Rating (GAWR) of the front or
rear axle.
Add-On Equipment
When carrying removable items, a limit
on how many people carried inside the
vehicle may be necessary. Be sure to
weigh the vehicle before buying and
installing the new equipment.
Caution
Overloading the vehicle may cause
damage. Repairs would not be covered by
the vehicle warranty. Do not overload the
vehicle.
Remember not to exceed the Gross Axle
Weight Rating (GAWR) of the front or
rear axle.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 215
Use the rear edge of the load floor for
measurement purposes. The
recommended location for the cargo
center of gravity is in zone C for the
CWR. It is the point where the mass of
a body is concentrated and,
if suspended at that point, would
balance the front and rear.
Here is an example of proper truck and
camper match:
1.Camper Center of Gravity
2.Recommended Center of Gravity
Location Zone
When the truck is used to carry a
slide-in camper, the total cargo load of
the truck consists of the manufacturer's
camper weight figure, the weight of
installed additional camper equipment
not included in the manufacturer's
camper weight figure, the weight of
camper cargo, and the weight of
passengers in the camper. The total
cargo load should not exceed the truck's
cargo weight rating, and the camper's center of gravity (1) should fall within
the truck's recommended center of
gravity zone (2) when installed.
Any accessories or other equipment
that are added to the vehicle must be
weighed. Then, subtract this extra
weight from the CWR. This extra weight
may shorten the center of gravity zone
of the vehicle.
If the slide-in camper and its load
weighs less than the CWR, the center of
gravity zone for the vehicle may be
larger.
Secure loose items to prevent weight
shifts that could affect the balance of
the vehicle. When the truck-camper is
loaded, drive to a scale and weigh on
the front and on the rear wheels
separately to determine axle loads.
Individual axle loads should not exceed
either of the gross axle weight ratings
(GAWR). The total axle loads should not
exceed the vehicle's gross vehicle
weight rating (GVWR). These ratings are
given on the Certification/Tire label
attached to the B-pillar.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
220 Driving and Operating
Warning (Continued)
.Do not operate the vehicle with the
heater cord permanently attached to
the vehicle. Possible heater cord and
thermostat damage could occur.
.While in use, do not let the heater
cord touch vehicle parts or sharp
edges. Never close the hood on the
heater cord.
.Before starting the vehicle, unplug the
cord, reattach the cover to the plug,
and securely fasten the cord. Keep the
cord away from any moving parts.
5. Before starting the engine, be sure to unplug and store the cord.
The length of time the heater should remain
plugged in depends on several factors. Ask a
dealer in the area where you will be parking
the vehicle for the best advice on this.
Retained Accessory Power (RAP)
When the vehicle is turned from on to off,
the following features (if equipped) will
continue to function for up to 10 minutes,
or until the driver door is opened. These
features will also work when the vehicle is
on or in accessory mode:
.Infotainment System
.Power Windows (during RAP this
functionality will be lost when any door
is opened)
.Sunroof (during RAP this functionality will
be lost when any door is opened)
.Auxiliary Power Outlet
.Audio System
.OnStar System
Vehicle Shutdown
Your vehicle is equipped with a sophisticated
on-board system to diagnose any potential
issues. Many of these operations can occur
after you shut off the engine. You may hear
fans, pumps, solenoids, etc. running for an
extended period after you shut down.
Shifting Into Park
{Warning
Parking on grades with poor traction such
as ice, snow, mud, or gravel may cause
the vehicle to unintentionally move and
could result in injury, death, and/or
vehicle damage. If equipped with
four-wheel drive, use AUTO or 4 (High) to
provide additional traction. Be sure to
apply the parking brake. See Electric
Parking Brake 0234 and
Four-Wheel Drive 0228.
{Warning
It can be dangerous to get out of the
vehicle if the shift lever is not fully in
P (Park) with the parking brake firmly set.
The vehicle can roll. If you have left the
engine running, the vehicle can move
suddenly. You or others could be injured.
To be sure the vehicle will not move,
even when you are on fairly level ground,
use the steps that follow. With
four-wheel drive, if the transfer case is in
N (Neutral), the vehicle will be free to
(Continued)

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
276 Driving and Operating
Caution
If a new fuel cap is needed, get the right
type of cap from your dealer. The wrong
type of fuel cap may not fit properly,
may turn on the malfunction indicator
lamp, and could damage the fuel system
and emissions system. SeeMalfunction
Indicator Lamp (Check Engine Light) 0122.
Filling a Portable Fuel Container
{Warning
Never fill a portable fuel container while
it is in the vehicle. Static electricity
discharge from the container can ignite
the fuel vapor. You or others could be
badly burned and the vehicle could be
damaged. To help avoid injury to you
and others:
.Dispense fuel only into approved
containers.
.Do not fill a container while it is
inside a vehicle, in a vehicle's trunk, in
a pickup bed, or on any surface other
than the ground.
(Continued)
Warning (Continued)
.Bring the fill nozzle in contact with
the inside of the fill opening before
operating the nozzle. Maintain contact
until filling is complete.
.Keep sparks, flames, and smoking
materials away from fuel.
.Avoid using electronic devices while
pumping fuel.
.When transporting a fuel container or
other material that can catch fire in
the truck bed, secure the container to
prevent spills.
Trailer Towing
General Towing Information
Only use towing equipment that has been
designed for the vehicle. Contact your dealer
or trailering dealer for assistance with
preparing the vehicle to tow a trailer. Read
the entire section before towing a trailer.
To tow a disabled vehicle, see Transporting
a Disabled Vehicle 0379. To tow the vehicle
behind another vehicle such as a motor
home, see Recreational Vehicle Towing
0 380.
Driving Characteristics and
Towing Tips
{Warning
You can lose control when towing a
trailer if the correct equipment is not
used or the vehicle is not driven properly.
For example, if the trailer is too heavy or
the trailer brakes are inadequate for the
load, the vehicle may not stop as
expected. You and others could be
seriously injured. The vehicle may also be
damaged, and the repairs would not be
covered by the vehicle warranty. Pull a
trailer only if all the steps in this section
have been followed. Ask your dealer for
advice and information about towing a
trailer with the vehicle.
Driving with a Trailer
Trailering is different than just driving the
vehicle by itself. Trailering affects handling,
acceleration, braking, and durability.
Successful and safe trailering requires proper
use of the correct equipment.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
278 Driving and Operating
and attachments, safety chains, electrical
connectors, lamps, tires, and mirrors. See
Towing Equipment0284. If the trailer has
electric brakes, start the combination
moving and then manually apply the trailer
brake controller to check that the trailer
brakes work. During the trip, occasionally
check that the cargo and trailer are secure
and that the lamps and any trailer brakes
are working.
Towing with a Stability Control System
When towing, the stability control system
might be heard. The system reacts to
vehicle movement caused by the trailer,
which mainly occurs during cornering. This is
normal when towing heavier trailers.
Following Distance
Stay at least twice as far behind the vehicle
ahead as you would when driving without a
trailer. This can help to avoid heavy braking
and sudden turns.
Passing
More passing distance is needed when
towing a trailer. The combination of the
vehicle and trailer will not accelerate as
quickly and is much longer than the vehicle
alone. It is necessary to go much farther beyond the passed vehicle before returning
to the lane. Pass on level roadways. Avoid
passing on hills if possible.
Backing Up
Hold the bottom of the steering wheel with
one hand. To move the trailer to the left,
move that hand to the left. To move the
trailer to the right, move that hand to the
right. Always back up slowly and, if possible,
have someone guide you.
Making Turns
Caution
Turn more slowly and make wider arcs
when towing a trailer to prevent damage
to your vehicle. Making very sharp turns
could cause the trailer to contact the
vehicle.
Make wider turns than normal when towing,
so the trailer will not go over soft shoulders,
over curbs, or strike road signs, trees,
or other objects. Always signal turns well in
advance. Do not steer or brake suddenly.
Driving on Grades
Reduce speed and shift to a lower gear
before starting down a long or steep
downhill grade. If the transmission is not
shifted down, the brakes may overheat and
result in reduced braking efficiency.
The vehicle can tow in D (Drive). Shift the
transmission to a lower gear if the
transmission shifts too often under heavy
loads and/or hilly conditions.
When towing at higher altitudes, engine
coolant will boil at a lower temperature
than at lower altitudes. If the engine is
turned off immediately after towing at high
altitude on steep uphill grades, the vehicle
could show signs similar to engine
overheating. To avoid this, let the engine
run, preferably on level ground, with the
transmission in P (Park) for a few minutes
before turning the engine off. If the
overheat warning comes on, see Engine
Overheating 0321.
Viewing Systems
If equipped, the viewing systems on the
vehicle can improve visibility while hitching,
backing, and driving with a trailer. See
Advanced Driver Assistance Systems 0252.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
284 Driving and Operating
The trailer load balance percentage is
calculated as: weight (1) divided by
weight (2) times 100.
After loading the trailer, separately weigh
the trailer and then the trailer tongue and
calculate the trailer load balance percentage
to see if the weights and distribution are
appropriate for your vehicle. If the trailer
weight is too high, it may be possible to
transfer some of the cargo into your vehicle.
If the trailer tongue weight is too high or
too low, it may be possible to rearrange
some of the cargo inside of the trailer.
Do not exceed the maximum allowable
tongue weight for your vehicle. Use the
shortest hitch extension available to position
the hitch ball closer to your vehicle. This will
help reduce the effect of the trailer tongue
weight on the trailer hitch and the rear axle.
If a cargo carrier is used in the trailer hitch
receiver, choose a carrier that positions the
load as close to the vehicle as possible.
Make sure the total weight, including the
carrier, is no more than half of the
maximum allowable tongue weight for the
vehicle or 227 kg (500 lb), whichever is less.Rear Gross Axle Weight Rating
(GAWR-RR)
The GAWR-RR is the total weight that can be
supported by the rear axle of the vehicle. Do
not exceed the GAWR-RR for the vehicle,
with the tow vehicle and trailer fully loaded
for the trip including the weight of the
trailer tongue. If using a weight-distributing
hitch, do not exceed the GAWR-RR before
applying the weight distribution spring bars.
The GAWR-RR for the vehicle is on the
Trailering Information Label.
Ask your dealer for trailering information or
assistance.
Towing Equipment
Hitches
{Warning
In order to avoid serious injury or
property damage, always follow the hitch
manufacturer's instructions when securing
your draw bar/coupling device to the
vehicle's hitch receiver.
Ensure that the draw bar/coupling device
is secured with a locking retainer pin or
other means such that rotation of the pin
or locking mechanism will not cause the
pin to back out or loosen during use.
Failure to correctly secure the draw bar/
coupling device to the receiver can result
in separation of the hitch/receiver while
towing.
Conventional Hitch
A conventional hitch is bolted to the frame
or cross member of the tow vehicle, and is
generally rated Class 2, 3, or 4.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 305
On the pop-up, touch Remove to remove the
Trailer Profile from the vehicle. Touch Cancel
to dismiss the pop-up and return to the
previous view.
Remove is displayed if there is a connected
OnStar plan active with the vehicle.
Removing a trailer profile will remove the
profile from the vehicle but the profile will
still be associated with the user account.
However, if there is not a connected OnStar
plan, then the remove button will read
DELETE and the profile will be deleted
permanently.
Set as Default Trailer
Touch Set as Default Trailer to select the
current profile as default.
The default Trailer profile will be
automatically selected each time a new
connection is detected. The Trailer Detection
Alert will no longer appear.
If this setting is turned off, the current
trailer profile is not the default trailer.GCW Alerts
Touch GCW Alert to turn on/off the GCW
Alert for the selected profile. These alerts
are based on the Trailer Profile, so the
settings for each Trailer Profile must be
turned on or off.
Turn this setting off to not receive GCW
Alerts in the DIC when that Trailer Profile is
active.
Maintenance Alerts
Touch Maintenance Alert to turn on/off
Maintenance Alerts for the selected profile.
These alerts are based on the Trailer Profile,
so the settings for each Trailer Profile must
be turned on or off.
All Maintenance Alerts for that active Trailer
Profile will be received when the setting
is on.
Turn this setting off to dismiss Maintenance
Alerts when that Trailer Profile is active.
Theft Alert
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 to turn on/off Theft Alerts
for the selected profile. These alerts are
based on the Trailer Profile, so the settings
for each Trailer Profile must be turned on
or off.
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 the smartphone
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
Driver
Mode Control 0238.
Touch Tow/Haul Mode Reminder to turn
on/off Tow/Haul Mode reminders for the
selected profile. These alerts are based on
the Trailer Profile, so the settings for each
Trailer Profile must be turned on or off.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/7/22
Vehicle Care 321
{Warning
Steam and scalding liquids from a hot
cooling system are under pressure.
Turning the pressure cap, even a little,
can cause them to come out at high
speed and you could be burned. Never
turn the cap when the cooling system,
including the pressure cap, is hot. Wait
for the cooling system and pressure cap
to cool.
Caution
Failure to follow the specific coolant fill
procedure could cause the engine to
overheat and could cause system
damage. If coolant is not visible in the
surge tank, contact your dealer.
If no coolant is visible in the surge tank, add
coolant.
1. Remove the coolant surge tank pressure cap when the cooling system, including
the coolant surge tank pressure cap and
upper radiator hose, is no longer hot.
Turn the pressure cap slowly
counterclockwise about one full turn. If a
hiss is heard, wait for that to stop.
A hiss means there is still some
pressure left.
2. Keep turning the pressure cap slowly, and remove it.
3. Fill the coolant surge tank with the proper mixture to the full cold mark.
4. With the coolant surge tank pressure cap off, start the engine and let it run until
the engine coolant temperature gauge
indicates approximately 90 °C (195 °F).
By this time, the coolant level inside the
coolant surge tank may be lower. If the
level is lower, add more of the proper
mixture to the coolant surge tank until
the level reaches the indicated mark.
5. Replace the pressure cap tightly.
6. Verify coolant level after the engine is shut off and the coolant is cold.
If necessary, repeat coolant fill procedure
Steps 1–6.Caution
If the pressure cap is not tightly installed,
coolant loss and engine damage may
occur. Be sure the cap is properly and
tightly secured.
Engine Overheating
If the vehicle has the Duramax diesel
engine, see the Duramax diesel supplement.
Caution
Do not run the engine if there is a leak
in the engine cooling system. This can
cause a loss of all coolant and can
damage the system and vehicle. Have
any leaks fixed right away.
The vehicle has several indicators to warn of
engine overheating.
There is a coolant temperature gauge in the
vehicle's instrument cluster. See Engine
Coolant Temperature Gauge 0118.
In addition, there are ENGINE OVERHEATED
STOP ENGINE, ENGINE OVERHEATED IDLE
ENGINE, and ENGINE POWER IS REDUCED
messages in the Driver Information
Center (DIC).