2023 GMC SIERRA ECU

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
Driving and Operating 297
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 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. SeeTow/Haul
Mode 0234.
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 vehicle
is turned on a reminder will appear to turn
on Tow/Haul Mode when the Trailer Profile
is active.
If Tow/Haul Mode is on and this setting is
on for a Trailer Profile, the reminder will not
appear when the Trailer Profile is active.
Trailer Length Indicator
Touch Trailer Length Indicator to view the
Trailer Length Indicator settings page. If this
setting is ON a guideline is displayed in the side mirror camera view to indicate the rear
of the attached trailer. If this setting is OFF
the guideline will not be displayed.
This setting will default to OFF if the trailer
length indicator feature is not set up. See
"Towing Assistance" for details on the setup.
Conversions and Add-Ons
Add-On Electrical Equipment
{Warning
The Data Link Connector (DLC) is used for
vehicle service and Emission Inspection/
Maintenance testing. See
Malfunction
Indicator Lamp (Check Engine Light) 0120
. A device connected to the DLC —such
as an aftermarket fleet or driver-behavior
tracking device —may interfere with
vehicle systems. This could affect vehicle
operation and cause a crash. Such devices
may also access information stored in the
vehicle’s systems.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/18/22
Vehicle Care 313
{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 0117.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/18/22
320 Vehicle Care
Extended Storage: Remove the black,
negative (−) cable from the battery or use a
battery trickle charger.
Negative Battery Cable Disconnection
{Warning
Before disconnecting the negative battery
cable, turn off all features, turn the
ignition off, and remove the key,
if equipped, from the vehicle. If this is
not done, you or others could be injured,
and the vehicle could be damaged.
Caution
If the battery is disconnected with the
ignition on or the vehicle in Retained
Accessory Power (RAP), the OnStar
back-up battery will be permanently
discharged and will need to be replaced.
1. Make sure the lamps, features, and accessories are turned off.
2. Turn the ignition off and remove the key, if equipped.
1. Loosen the negative battery cable nut (1).
2. Remove the negative battery cableclamp (2) from the negative battery post.
3. Cover the negative battery cable clamp, and negative battery post with a
non-conductive material to prevent any
contact with the negative battery cable.
Negative Battery Cable Reconnection
Caution
When reconnecting the battery:
.Use the original nut from the vehicle
to secure the negative battery cable.
Do not use a different nut. If you
need a replacement nut, see your
dealer.
.Tighten the nut with a hand tool. Do
not use an impact wrench or power
tools to tighten the nut.
The vehicle could be damaged if these
guidelines are not followed.
Caution
Do not use paints, lubricants, or corrosion
inhibitors on the nut that secures the
negative battery cable to the vehicle. This
could damage the vehicle.
1. Install the negative battery cable clamp to the negative battery post.
2. Tighten the negative battery cable nut.
3. Turn the ignition on.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/18/22
Vehicle Care 349
Replace the tire if:
.The indicators at three or more
places around the tire can be seen.
.There is cord or fabric showing
through the tire's rubber.
.The tread or sidewall is cracked, cut,
or snagged deep enough to show
cord or fabric.
.The tire has a bump, bulge, or split.
.The tire has a puncture, cut, or other
damage that cannot be repaired well
because of the size or location of the
damage.
Tire Rotation
Tires should be rotated according to the
interval listed in the maintenance
schedule. SeeMaintenance Schedule
0 385.
Tires are rotated to achieve a more
uniform wear for all tires. The first
rotation is the most important.
Anytime unusual wear is noticed, rotate
the tires as soon as possible, check for
proper tire inflation pressure, and check for damaged tires or wheels. If the
unusual wear continues after the
rotation, check the wheel alignment.
See
When It Is Time for New Tires 0351
and
Wheel Replacement 0354.
If the full-size spare tire is part of the
tire rotation, make sure the tire rotated
into the spare position is stored
securely. Push, pull, and then try to
rotate or turn the tire. If it moves, use
the wheel wrench/hoist shaft to tighten
the cable. See Tire Changing0357.
Use this rotation pattern when rotating
the tires if the vehicle has single rear
wheels.
Dual Tire Rotation
When the vehicle is new, or whenever a
wheel, wheel bolt, or wheel nut is
replaced or serviced, check the wheel
nut torque after 160, 1 600, and
10 000 km (100, 1,000, and 6,000 mi) of
driving. For proper torque and wheel
nut tightening information, see “Wheel
Nut Torque” underCapacities and
Specifications 0393 and “Removing the
Flat Tire and Installing the Spare Tire”
under Tire Changing 0357.
The outer tire on a dual wheel setup
generally wears faster than the inner
tire. Tires last longer and wear more
evenly if they are rotated. See Tire
Inspection 0348 and
Tire Rotation 0349. Also see
Maintenance Schedule 0385.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/18/22
Vehicle Care 355
Your dealer will know the kind of wheel that
is needed.
Each new wheel should have the same
load-carrying capacity, diameter, width,
offset, and be mounted the same way as
the one it replaces.
Replace wheels, wheel bolts, wheel nuts,
or Tire Pressure Monitor System (TPMS)
sensors with new GM original equipment
parts.
{Warning
Using the wrong replacement wheels,
wheel bolts, or wheel nuts can be
dangerous. It could affect the braking and
handling of the vehicle. Tires can lose air
and cause loss of control, resulting in a
crash. Always use the correct wheel,
wheel bolts, and wheel nuts for
replacement.
{Warning
Replacing a wheel with a used one is
dangerous. How it has been used or how
far it has been driven may be unknown.(Continued)
Warning (Continued)
It could fail suddenly and cause a crash.
When replacing wheels, use a new GM
original equipment wheel.
Caution
The wrong wheel can also cause
problems with bearing life, brake cooling,
speedometer or odometer calibration,
headlamp aim, bumper height, vehicle
ground clearance, and tire or tire chain
clearance to the body and chassis.
Tire Chains
{Warning
If the vehicle has LT275/65R20 size tires,
do not use tire chains. There is not
enough clearance. Tire chains used on a
vehicle without the proper amount of
clearance can cause damage to the
brakes, suspension, or other vehicle parts.
The area damaged by the tire chains
could cause loss of control and a crash.
Use another type of traction device only(Continued)
Warning (Continued)
if its manufacturer recommends it for the
vehicle's tire size combination and road
conditions. Follow that manufacturer's
instructions. To avoid vehicle damage,
drive slow and readjust or remove the
traction device if it is contacting the
vehicle. Do not spin the wheels.
If traction devices are used, install them
on the rear tires.
Caution
Use tire chains only where legal and only
when necessary. Use chains that are the
proper size for the tires. If the vehicle has
LT235/80R17 size tires, install the chains
on the tires of the rear axle only. If the
vehicle has LT245/75R17, LT265/70R17,
or LT275/70R18 size tires, install the
chains on the tires of the front and rear
axle. Tighten them as tightly as possible
with the ends securely fastened. Drive
slowly and follow the chain
manufacturer's instructions. If the chains
contact the vehicle, stop and retighten
them. If the contact continues, slow
(Continued)

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/18/22
Vehicle Care 361
Rear Position
5. If the flat tire is on the rear of the vehicle, position the jack under the rear
axle between the spring anchor and the
shock absorber bracket.
If a snow plow has been added to the
front of the vehicle, lower the snow
plow fully before raising the vehicle.
Make sure that the jack head is
positioned so that the rear axle is resting
securely between the grooves that are
on the jack head.
{Warning
Getting under a vehicle when it is lifted
on a jack is dangerous. If the vehicle slips
off the jack, you could be badly injured
or killed. Never get under a vehicle when
it is supported only by a jack.
{Warning
Raising the vehicle with the jack
improperly positioned can damage the
vehicle and even make the vehicle fall. To
help avoid personal injury and vehicle
damage, be sure to fit the jack lift head
into the proper location before raising
the vehicle.
{Warning
The jack has a feature to limit its travel
to prevent overextension. When the
height limit is reached, an increase in
resistance if felt when attempting to
raise the jack farther. Raising the jack
past the height limit can damage the jack
pin and cause the jack to lock into an
(Continued)
Warning (Continued)
overextended position or not lower fully.
Do not attempt to force the jack higher
once the height limit is reached.
6. Turn the wheel wrench clockwise to raise the vehicle. Raise the vehicle far enough
off the ground so there is enough room
for the spare tire to fit under the
wheel well.
7. Remove all the wheel nuts and take offthe flat tire.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/18/22
Vehicle Care 363
Warning (Continued)
accessory locking wheel nuts. See
Capacities and Specifications0393 for
original equipment wheel nut torque
specifications.
Caution
Improperly tightened wheel nuts can lead
to brake pulsation and rotor damage. To
avoid expensive brake repairs, evenly
tighten the wheel nuts in the proper
sequence and to the proper torque
specification. See Capacities and
Specifications 0393 for the wheel nut
torque specification.
13. Tighten the nuts firmly in a crisscross sequence, as shown, by turning the
wheel wrench clockwise.
For vehicles with dual wheels, have a
technician check the wheel nut tightness of
all wheels with a torque wrench after the
first 160, 1 600 and 10 000 km (100, 1,000
and 6,000 mi). Repeat this service whenever
you have a tire removed or serviced. See
Capacities and Specifications 0393.
When reinstalling the regular wheel and tire,
also reinstall either the center cap,
or bolt-on hub cap, depending on what the
vehicle is equipped with. For center caps,
place the cap on the wheel and tap it into
place until it seats flush with the wheel. The
cap only goes on one way. Be sure to line
up the tab on the center cap with the
indentation on the wheel. For bolt-on hub
caps, align the plastic nut caps with the
wheel nuts and then tighten by hand. Then
use the wheel wrench to tighten.Storing a Flat or Spare Tire and Tools
{Warning
Storing a jack, a tire, or other equipment
in the passenger compartment of the
vehicle could cause injury. In a sudden
stop or collision, loose equipment could
strike someone. Store all these in the
proper place.
{Warning
Failure to follow these tire storage
instructions carefully could result in
personal injury or property damage if the
hoist cable fails or if the tire comes loose.
Make sure the tire is stored securely
before driving.
Caution
Storing an aluminum wheel with a flat
tire under your vehicle for an extended
period of time or with the valve stem
pointing up can damage the wheel.
Always stow the wheel with the valve
stem pointing down and have the
wheel/tire repaired as soon as possible.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/18/22
366 Vehicle Care
9. Make sure the tire is stored securely.Push, pull, and then try to turn the tire.
If the tire moves, use the wheel wrench
to tighten the cable.
If equipped with a spare tire cable,
reattach the clip to the frame
attachment bracket. Note that there may
be slack in the cable.
Repeat this tightness check procedure
when checking the spare tire pressure
according to the scheduled maintenance
information or any time the spare tire is
handled due to service of other
components.
Correctly Stored
Incorrectly Stored
10. Reinstall the spare tire lock, if the vehicle has one.
Return the jack and tools to their original
location in the vehicle. See “Removing the
Spare Tire and Tools.”