towing GMC SIERRA 2024 User Guide

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 223
Warning (Continued)
.The vehicle exhaust system has been
modified, damaged, or improperly
repaired.
.There are holes or openings in the
vehicle body from damage or
aftermarket modifications that are not
completely sealed.
If unusual fumes are detected or if it is
suspected that exhaust is coming into the
vehicle:
.Drive it only with the windows
completely down.
.Have the vehicle repaired immediately.
Never park the vehicle with the engine
running in an enclosed area such as a
garage or a building that has no fresh air
ventilation.
Running the Vehicle While Parked
It is better not to park with the engine
running.
If the vehicle is left with the engine running,
follow the proper steps to be sure the
vehicle will not move. See Shifting Into Park
0 220 and
Engine Exhaust 0222.
If parking on a hill and pulling a trailer, see
Driving Characteristics and Towing Tips
0 276.
Automatic Transmission
If equipped, there is an electronic shift lever
position indicator within the instrument
cluster. This display comes on when the
ignition is in accessory mode, on,
or service mode.
There are several different positions for the
shift lever.
See Driver Mode Control 0238 and “Range
Selection Mode” underManual Mode 0226.
P : This position locks the rear wheels. Use
P (Park) when starting the engine because
the vehicle cannot move easily.
When parked on a hill, especially when the
vehicle has a heavy load, you might notice
an increase in the effort to shift out of
P (Park). See “Torque Lock” underShifting
Into Park 0220.
{Warning
It is 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.
Do not leave the vehicle when the engine
is running. 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,
always set the parking brake and move
the shift lever to P (Park). See Shifting
Into Park 0220 and
Driving Characteristics and Towing Tips
0 276.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 225
Use D (Drive) and Tow/Haul Mode when
towing a trailer, carrying a heavy load,
driving on steep hills, or driving off-road.
Shift the transmission to a lower gear if the
transmission shifts too often.
Downshifting the transmission in slippery
road conditions could result in skidding. See
“Skidding”underLoss of Control 0202.
The vehicle has a shift stabilization feature
that adjusts the transmission shifting to the
current driving conditions in order to reduce
rapid upshifts and downshifts. This shift
stabilization feature is designed to
determine, before making an upshift, if the
engine is able to maintain vehicle speed by
analyzing things such as vehicle speed,
throttle position, and vehicle load. If the
shift stabilization feature determines that a
current vehicle speed cannot be maintained,
the transmission does not upshift and
instead holds the current gear. In some
cases, this could appear to be a delayed
shift, however the transmission is operating
normally. Grade Braking is available in all modes,
including Range Selection Mode. See
Manual
Mode 0226. Grade Braking assists in
maintaining desired vehicle speeds when
driving on downhill grades by using the
engine and transmission to slow the vehicle.
The transmission uses adaptive shift
controls. The adaptive shift control process
continually compares key shift parameters
to pre-programmed ideal shifts stored in the
transmission’s computer. The transmission
constantly makes adjustments to improve
vehicle performance according to how the
vehicle is being used, such as with a heavy
load or when the temperature changes.
During this adaptive shift control process,
shifting might feel different as the
transmission determines the best settings.
When temperatures are very cold, the
transmission's gear shifting may be delayed
to provide more stable shifts until the
engine warms up. Shifts could be more
noticeable with a cold transmission. This
difference in shifting is normal. L :
This position allows selection of a range
of gears appropriate for current driving
conditions. If equipped, see “Range Selection
Mode” underManual Mode 0226.
Caution
Spinning the tires or holding the vehicle
in one place on a hill using only the
accelerator pedal may damage the
transmission. The repair will not be
covered by the vehicle warranty. If the
vehicle is stuck, do not spin the tires.
When stopping on a hill, use the brakes
to hold the vehicle in place.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
226 Driving and Operating
Manual Mode
Range Selection Mode
Range Selection Mode helps control the
vehicle transmission and vehicle speed while
driving downhill or towing a trailer.
It permits the manual selection of a desired
gear range.
To use this feature:1. Move the shift lever to L (Manual Mode).
2. Press the plus/minus buttons on the shift lever to select the desired gear
range for current driving conditions. When the shift lever is moved from
D (Drive) to L (Manual Mode), a number
displays next to the L, indicating the current
transmission range.
This number is the highest gear that the
transmission will allow while operating in
L (Manual Mode). All gears below that
number are available. As driving conditions
change, the transmission can automatically
shift to lower gears. For example, when L5 is
selected, 1 (First) through 5 (Fifth) gears are
automatically shifted by the transmission,
but 6 (Sixth) cannot be used until the plus/
minus button on the shift lever is used to
change to the range.
In vehicles with gasoline engines, when the
shift lever is moved from D (Drive) to
L (Manual Mode), a downshift may occur.
The gear that the transmission is operating
in when the shift lever is moved from D
(Drive) to L (Manual Mode) determines if a
downshift occurs. See the following chart.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 227
10-Speed Automatic TransmissionGear before shifting from D (Drive) to L (Manual Mode) 10th 9th 8th 7th 6th 5th 4th 3rd 2nd 1st
Range after shifting from D (Drive) to L (Manual
Mode) –Tow/Haul not engaged L7 L7 L7 L6 L5 L4 L3 L3 L2 L1
Range after shifting from D (Drive) to L (Manual
Mode) –Tow/Haul engaged L7 L7 L6 L5 L4 L3 L3 L3 L2 L1
Tow/Haul Mode
The Tow/Haul Mode adjusts the
transmission shift pattern to reduce shift
cycling. This provides increased performance,
vehicle control, and enhanced transmission
and engine cooling when driving down steep
hills or mountain grades, when towing,
or when hauling heavy loads. See
Driver
Mode Control 0238 to activate Tow/
Haul Mode.
For vehicles without Driver Mode Control,
press the Tow/Haul button on the center
stack. If equipped with Active Hydraulic Assist, the
vehicle will provide a stiffer steering
response when Tow/Haul Mode is engaged
to provide enhanced steering functionality.
Tow/Haul Mode Grade Braking
Grade Braking is available in all modes,
including Range Selection Mode. See
Manual
Mode 0226. Grade Braking assists in
maintaining desired vehicle speeds when
driving on downhill grades by using the
engine and transmission to slow the vehicle.
See Towing Equipment 0284.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 229
When the shift is complete the indicator will
stop flashing. The DIC message turns off
once the shift is complete. If the transfer
case cannot complete a shift request, it will
go back to its last chosen setting.
The settings are:
N (Neutral) :Use only when the vehicle
needs to be towed. See Recreational Vehicle
Towing 0380 or
Transporting a Disabled Vehicle 0379.
2
m(Two-Wheel Drive High) : Use for driving
on most streets and highways. The front
axle is not engaged. This setting provides
the best fuel economy.
AUTO (Automatic Four-Wheel Drive) : Use
when road surface conditions are variable.
When driving in AUTO, the front axle is
engaged, and the vehicle's power is sent to
the front and rear wheels automatically
based on driving conditions. This setting
provides slightly lower fuel economy
than 2
m.
4
m(Four-Wheel Drive High) : Use this
setting when extra traction is needed, such
as when driving on snowy or icy roads,
when off-roading, or when plowing snow. 4
n(Four-Wheel Drive Low) :
This setting
engages the front axle and delivers extra
torque. Choose 4
nwhen driving off-road in
deep sand, deep mud, or deep snow, and
while climbing or descending steep hills.
While driving in 4
n, keep vehicle speed
below 60 km/h (36 mph).
Shifting into 4
nwill turn Traction Control
and StabiliTrak/ESC off. See Traction Control/
Electronic Stability Control 0236.
Shifts between 2
m, 4m, and AUTO
Any of these shifts can be made at normal
driving speed.
The actual 4x4 shift request is only made
after the button is released. The
4x4 indicator will remain flashing until the
shift request has completed. A DIC message
displays to indicate that the 4x4 transfer
case has been requested to shift to the new
desired state.
Once the 4x4 shift has completed, the DIC
message disappears, the 4x4 indicator stops
flashing, and the current setting is indicated.
When a shift to 2
mis completed successfully
while in P (Park), the parking brake will
engage. To resume driving, shift the transmission to the desired gear and
manually release the parking brake or press
the accelerator pedal to begin driving. See
Electric Parking Brake
0234.
If equipped, use 4
n, AUTO, or 4mto provide
additional traction when parking on a steep
grade with poor traction such as ice, snow,
mud, or gravel.
Shifting Into 4
n
1. The ignition must be on and the vehicle must be stopped or moving less than
5 km/h (3 mph) with the transmission in
N (Neutral). It is best for the vehicle to
be moving 1.6 to 3.2 km/h (1 to 2 mph).
2. Press 4
n. The actual 4x4 shift request is
only made after the button is released.
The 4x4 indicator will remain flashing
until the shift request has completed.
A DIC message displays to indicate that
the 4x4 transfer case has been requested
to shift to the new desired state.
Once the 4x4 shift has completed, the
DIC message disappears, the
4x4 indicator stops flashing and the
current setting is indicated.
If vehicle speed is higher when shift request
occurs, a DIC message displays. Reduce
vehicle speed.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 231
Shifting Out of N (Neutral)
To shift out of N (Neutral):1. Turn the ignition on with the engine off. See Ignition Positions 0216.
2. Set the parking brake. See Electric
Parking Brake 0234.
3. Shift the transmission to N (Neutral).
4. Shift the transfer case to 2
m. Transfer
case shifts out of N (Neutral) can only be
made into 2
m. When the shift to 2mis
complete, the indicator in the instrument
cluster will stop flashing. If the transfer
case cannot complete a shift, the
indicator will return to the previously
selected setting.
Part-time Transfer Case
Two-Speed Transfer Case
Work Truck Shown, All Other Models Similar
If equipped, the transfer case controls are
used to shift into and out of four-wheel
drive.
To shift the transfer case, press the desired
button. The indicator in the instrument
cluster will flash while a shift is in progress.
The indicator displayed will change to
indicate the setting requested. When the shift is complete the indicator will
stop flashing. The DIC message turns off
once the shift is complete. If the transfer
case cannot complete a shift request, it will
go back to its last chosen setting.
The settings are:
N (Neutral) :
Use only when the vehicle
needs to be towed. See Recreational Vehicle
Towing 0380 or
Transporting a Disabled Vehicle 0379.
2
m(Two-Wheel Drive High) : Use for driving
on most streets and highways. The front
axle is not engaged. This setting provides
the best fuel economy.
4
m(Four-Wheel Drive High) : Use this
setting when extra traction is needed, such
as when driving on snowy or icy roads,
when off-roading, or when plowing snow.
4
n(Four-Wheel Drive Low) : This setting
engages the front axle and delivers extra
torque. Choose 4
nwhen driving off-road in
deep sand, deep mud, or deep snow, and
while climbing or descending steep hills.
While driving in 4
n, keep vehicle speed
below 60 km/h (36 mph).

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 235
If the EPB is applied while the vehicle is
moving, the vehicle will decelerate as long
as the switch is pressed. If the switch is
pressed until the vehicle comes to a stop,
the EPB will remain applied.
The vehicle may automatically apply the EPB
in some situations when the vehicle is not
moving. This is normal, and is done to
periodically check the correct operation of
the EPB system, or at the request of other
safety functions that utilize the EPB.
If the EPB fails to apply, block the rear
wheels to prevent vehicle movement.
EPB Release
To release the EPB:1. Turn the ignition on or to accessory mode.
2. Apply and hold the brake pedal.
3. Press the EPB switch momentarily.
The EPB is released when the red parking
brake status light is off.
If the amber service parking brake warning
light is on, release the EPB by pressing and
holding the EPB switch. Continue to hold the
switch until the red parking brake status
light is off. If either light stays on after
release is attempted, see your dealer.
Caution
Driving with the parking brake on can
overheat the brake system and cause
premature wear or damage to brake
system parts. Make sure that the parking
brake is fully released and the brake
warning light is off before driving.
If you are towing a trailer and parking on a
hill, see Driving Characteristics and Towing
Tips 0276.
Automatic EPB Release
The EPB will automatically release if the
vehicle is running, placed into gear, and an
attempt is made to drive away. Avoid rapid
acceleration when the EPB is applied, to
preserve parking brake lining life.
Brake Assist
Brake Assist detects rapid brake pedal
applications due to emergency braking
situations and provides additional braking to
activate the Antilock Brake System (ABS) if
the brake pedal is not pushed hard enough
to activate ABS normally. Minor noise, brake
pedal pulsation, and/or pedal movement
during this time may occur. Continue to apply the brake pedal as the driving
situation dictates. Brake Assist disengages
when the brake pedal is released.
Hill Start Assist (HSA)
{Warning
Do not rely on the HSA feature. HSA does
not replace the need to pay attention
and drive safely. You may not hear or
feel alerts or warnings provided by this
system. Failure to use proper care when
driving may result in injury, death,
or vehicle damage. See
Defensive Driving
0 200.
When the vehicle is stopped on a grade, Hill
Start Assist (HSA) prevents the vehicle from
rolling in an unintended direction during the
transition from brake pedal release to
accelerator pedal apply. The brakes release
when the accelerator pedal is applied. If the
accelerator pedal is not applied within a few
minutes, the Electric Parking Brake will
apply. The brakes may also release under
other conditions. Do not rely on HSA to hold
the vehicle.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 239
standard/default mode. There is no
persistent indicator in the instrument cluster
for this mode.
6Snow/Ice Mode :Snow/Ice Mode
improves vehicle acceleration on snow and
ice covered roads. When active, Snow/Ice
Mode will adjust acceleration to optimize
traction on slippery surfaces. This can
compromise the acceleration on dry asphalt.
This feature is not intended for use when
the vehicle is stuck in sand, mud, ice, snow,
or gravel. If the vehicle becomes stuck, see If
the Vehicle Is Stuck 0209.
7Off-Road Mode : Use this mode for
off-road recreational driving. Off-Road Mode
should be used to improve driving at
moderate speeds, on grass, gravel, dirt,
unpaved roads, or snow-covered roads. The
accelerator pedal is tuned for off-road use.
This mode modifies pedal mapping,
transmission shift pattern, Antilock Brake
System (ABS), StabiliTrak/Electronic Stability
Control (ESC), and Traction Control System
(TCS) performance.
For more information on off-road driving see
Off-Road Driving 0203.
_Tow/Haul Mode : Use this mode
when hauling heavy loads to provide
increased performance and vehicle control.
Tow/Haul Mode adjusts the transmission
shift pattern, trailer sway, and steering.
If the vehicle is turned off with Tow/Haul
Mode active and then restarted within four
hours or less, Tow/Haul will remain active.
Otherwise, the vehicle will start in
Normal Mode.
If the vehicle has a diesel engine, exhaust
braking is automatically activated when
Tow/Haul Mode is selected. It maintains
vehicle speed by automatically
implementing a shift pattern that uses the
engine and the transmission to slow the
vehicle. The system will command
downshifts and use the turbocharger on the
engine to reduce vehicle speed when the
brake is applied. The normal tow/haul shift
pattern will return once the vehicle is on a
low grade or when the accelerator pedal is
pressed.
While in the Electronic Range Select (ERS)
Mode, grade breaking is deactivated,
allowing the driver to select a range and
limiting the highest gear available. See
Manual Mode 0226. For more information on trailer weight
specifications, see
Towing Equipment 0284.
Locking Rear Axle
Vehicles with a locking rear axle can give
more traction on snow, mud, ice, sand,
or gravel. It works like a standard axle most
of the time, but when traction is low, this
feature will allow the rear wheel with the
most traction to move the vehicle.
Cruise Control
If equipped, cruise control allows the vehicle
to maintain a set speed of 40 km/h
(25 mph) or more without active
acceleration. Cruise control does not work at
speeds below about 40 km/h (25 mph).
{Warning
Cruise control can be dangerous where
you cannot drive safely at a steady
speed. Do not use cruise control on
winding roads or in heavy traffic.
Cruise control can be dangerous on
slippery roads. On such roads, fast
changes in tire traction can cause
(Continued)

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
250 Driving and Operating
When following a vehicle and entering a
curve, ACC may not detect the vehicle ahead
and accelerate to the set speed. When this
happens, the vehicle ahead indicator will not
appear.
ACC may detect a vehicle that is not in your
lane and apply the brakes.
ACC may occasionally provide an alert and/
or braking that is considered unnecessary.
It could respond to vehicles in different
lanes or stationary objects when entering or
exiting a curve. This is normal operation.
The vehicle does not need service.Other Vehicle Lane Changes
ACC will not detect a vehicle ahead until it
is completely in the lane. The brakes may
need to be manually applied.
Objects Not Directly in Front of Your Vehicle
The detection of objects in front of the
vehicle may not be possible if:
.The vehicle or object ahead is not within
your lane.
.The vehicle ahead is shifted, not centered,
or is shifted to one side of the lane.
Driving in Narrow Lanes
Vehicles in adjacent traffic lanes or roadside
objects may be incorrectly detected when
located along the roadway. Do Not Use ACC on Hills
Do not use ACC when driving on steep hills
as ACC may not detect a vehicle ahead.
Towing with ACC
If equipped when towing a trailer, ACC
driving characteristics such as following gap,
acceleration rates and braking rates may be
modified to provide a better towing
experience.
When ACC is used with vehicles equipped
with aftermarket trailer brake controller,
disengage ACC before applying the manual
trailer brake. ACC will not automatically
disengage when manual trailer brake is
applied.
ACC may be used when towing a trailer
when trailer attached is within GM-approved
allowable size and weight limits. See
Trailer
Towing 0280.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16908340) - 2024 - CRC - 12/13/22
Driving and Operating 251
When towing a trailer with ACC, it is
important to properly set the Trailer Gain.
See“Integrated Trailer Brake Control
System” inTowing Equipment 0284 for
Trailer Gain Adjustment Procedure.
Use Tow/Haul mode when driving down
steep hills or mountain grades, or when
hauling heavy loads. See Driver Mode
Control 0238.
Disengaging ACC
There are three ways to disengage ACC:
.Step lightly on the brake pedal.
.Press*.
.PressJ.
Erasing Speed Memory
The ACC set speed is erased from memory if
Jis pressed or if the ignition is turned off.
Weather Conditions Affecting ACC
If the interior temperature is extremely
high, the instrument cluster may indicate
that ACC is temporarily unavailable. This can
be caused by extreme hot weather
conditions with direct sunlight on the front
camera. ACC will return to normal operation
once the cabin temperature is lower. Conditions that are associated with low
visibility, such as fog, rain, snow, or road
spray, may limit ACC performance. Water
droplets from rain or snow that remain on
the windshield may also limit ACC’s ability
to detect objects.
System operation may be limited under
snow, heavy rain, or road spray conditions.
{Warning
Camera visibility may be limited and the
ACC system may not work properly if the
windshield is not clear. Do not use ACC if
moisture is present on the inside of the
windshield or the windshield washer is
used in cold weather. Turn on the front
defroster and make sure the windshield is
clear before using ACC. Before driving,
check that the windshield wipers are in
good condition and replace them if worn.
Lighting Conditions Affecting ACC
The ACC front camera can be affected by
poor lighting conditions, and ACC may have
limited performance when:
.There are changes in brightness, such as
entering and exiting tunnels, bridges, and
overpasses.
.Low sun angles cause the camera to not
detect objects, or it is more difficult to
detect objects in the same traffic lane.
.Lighting is poor in the evening or early
morning
.There are multiple changes in brightness
or shadows along the vehicle roadway.
.In a tunnel without the headlamps on,
or in a tunnel when there is a vehicle in
front that does not have its taillamps on.
.Subjected to strong light from opposing
lane traffic in the front of the vehicle,
such as high-beam headlamps from
oncoming traffic.
Accessory Installations and Vehicle
Modifications
Do not install or place any object around
the front camera windshield area that would
obstruct the front camera view.
Do not install objects on top of the vehicle
that overhang and obstruct the front
camera, such as a canoe, kayak, or other
items that can be transported on the
vehicle roof.
Do not modify the hood, headlamps, or fog
lamps, as this may limit the camera’s ability
to detect an object.