ECU GMC SIERRA DENALI 2020 Workshop Manual

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
324 Driving and Operating
.Make sure the weight on the
front and rear axles does not
exceed the axle rating for each.
. For the front axle, if more cargo
or passengers must be carried,
appropriate counter ballast must
be installed rear of the rear axle.
Counter ballast must be properly
secured so it will not move
during driving.
. Rear ballast may be required to
ensure a proper front and rear
weight distribution ratio, even
though the actual weight at the
front axle may be less than the
front axle rating.
. The snow plow manufacturer or
installer can assist in
determining the amount of rear
ballast required, to help make
sure the snow plow/vehicle
combination does not exceed
the GVW rating, the front and
rear axle ratings, and the front
and rear weight distribution ratio.
. The total vehicle must not
exceed the GVW rating. Front axle reserve capacity is the
difference between the Gross Axle
Weight Rating (GAWR) and the front
axle weight of the vehicle with full
fuel and passengers. This is the
amount of weight that can be added
to the front axle before reaching the
front GAWR.
United States
Canada
The front axle reserve capacity for
the vehicle is in the lower right
corner of the Certification/Tire label.
To calculate the amount of weight
any front accessory, such as a snow
plow, is adding to the front axle, use
this formula:

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 351
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 0133.
In addition, there are ENGINE
OVERHEATED STOP ENGINE,
ENGINE OVERHEATED IDLE
ENGINE, and ENGINE POWER IS
REDUCED messages in the Driver
Information Center (DIC).
If the decision is made not to lift the
hood when this warning appears,
get service help right away. See
Roadside Assistance Program
0 466.
If the decision is made to lift the
hood, make sure the vehicle is
parked on a level surface.
2.7L L4, 4.3L V6, 5.3L V8, and 6.2L
V8 Engines
Check to see if the engine cooling
fans are running. If the engine is
overheating, the fans should be
running. If they are not, do not
continue to run the engine and have
the vehicle serviced. If the engine or transmission detects
an impending hot fluid condition,
then the transmission may force
upshifts to limit temperatures.
Downshifts may also be prevented
in this instance. Normal operation
may continue unless the display
indicates there is a hot condition
and engine should be idled.
If Steam is Coming from the
Engine Compartment
{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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
360 Vehicle Care
For vehicles equipped with the Stop/
Start system:
1. Loosen and remove thenegative battery cable nut (1)
at the battery sensor
connection.
2. Remove the negative battery cable (2) from the battery
sensor stud.
3. Cover the negative battery cable terminal, battery sensor
stud, and negative battery post
with a non-conductive material
to prevent any contact with the
negative battery cable. For vehicles not equipped with the
Stop/Start system:1. Loosen the negative battery
cable nut (1).
2. Remove the negative battery cable clamp (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.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 399
If the full-size 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. SeeTire Changing 0407.
When It Is Time for New
Tires
Factors, such as maintenance,
temperatures, driving speeds,
vehicle loading, and road conditions
affect the wear rate of the tires.
Treadwear indicators are one way to
tell when it is time for new tires.
Treadwear indicators appear when
the tires have only 1.6 mm (1/16 in)
or less of tread remaining. Some
commercial truck tires may not have
treadwear indicators. See Tire
Inspection 0396 and
Tire Rotation 0396 for additional
information.
The rubber in tires ages over time.
This also applies to the spare tire,
if the vehicle has one, even if it is
never used. Multiple factors
including temperatures, loading
conditions, and inflation pressure
maintenance affect how fast aging
takes place. GM recommends that
tires, including the spare if
equipped, be replaced after six
years, regardless of tread wear. To
identify the age of a tire, use the tire
manufacture date which is the last
four digits of the DOT Tire
Identification Number (TIN) which is
molded into one side of the tire
sidewall. The first two digits
represent the week (01-52) and the
last two digits, the year. For example, the third week of the year
2010 would have a four-digit DOT
date of 0310.
Vehicle Storage
Tires age when stored normally
mounted on a parked vehicle. Park
a vehicle that will be stored for at
least a month in a cool, dry, clean
area away from direct sunlight to
slow aging. This area should be free
of grease, gasoline, or other
substances that can deteriorate
rubber.
Parking for an extended period can
cause flat spots on the tires that
may result in vibrations while
driving. When storing a vehicle for
at least a month, remove the tires or
raise the vehicle to reduce the
weight from the tires.
Buying New Tires
GM has developed and matched
specific tires for the vehicle. The
original equipment tires installed
were designed to meet General
Motors Tire Performance Criteria

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 405
Warning (Continued)
manufacturer's instructions. To
help avoid damage to the vehicle,
drive slowly, readjust, or remove
the device if it is contacting the
vehicle, and do not spin the
vehicle's wheels.
If you do find traction devices that
will fit, 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
265/70R17 or 265/65R18 size
tires, they may be installed on the
tires of the rear axle only. If the
vehicle is a dual rear wheel model
and has LT235/80R17 tires,
chains may be installed on the
tires of the rear axle only. If the(Continued)
Caution (Continued)
vehicle has 255/70R17,
LT245/75R17, or LT275/70R18
size tires, they may be installed
on the tires of the front and rear
axle. If the vehicle is a 2500
Series with LT265/70R17 size
tires, chains may be installed on
the tires of both 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 you can hear the
chains contacting the vehicle,
stop and retighten them. If the
contact continues, slow down
until it stops. Driving too fast or
spinning the wheels with chains
on will damage the vehicle.
If a Tire Goes Flat
It is unusual for a tire to blowout
while driving, especially if the tires
are maintained properly. If air goes
out of a tire, it is much more likely to leak out slowly. But if there ever is a
blowout, here are a few tips about
what to expect and what to do:
If a front tire fails, the flat tire
creates a drag that pulls the vehicle
toward that side. Take your foot off
the accelerator pedal and grip the
steering wheel firmly. Steer to
maintain lane position, and then
gently brake to a stop, well off the
road, if possible.
A rear blowout, particularly on a
curve, acts much like a skid and
may require the same correction as
used in a skid. Stop pressing the
accelerator pedal and steer to
straighten the vehicle. It may be
very bumpy and noisy. Gently brake
to a stop, well off the road,
if possible.
{Warning
Driving on a flat tire will cause
permanent damage to the tire.
Re-inflating a tire after it has been
driven on while severely
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
412 Vehicle Care
Rear Position All Other ModelsFor all other models, 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.
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 andtake off the flat tire.
{Warning
Rust or dirt on a wheel, or on
the parts to which it is
fastened, can make wheel
nuts become loose after time.
The wheel could come off and
cause a crash. When
changing a wheel, remove any
rust or dirt from places where
the wheel attaches to the
vehicle. In an emergency, a
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 415
Warning (Continued)
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(Continued)
Caution (Continued)
pointing down and have the
wheel/tire repaired as soon as
possible.
Caution
The tire hoist can be damaged if
there is no tension on the cable
when using it. To have the
necessary tension, the spare or
road tire and wheel assembly
must be installed on the tire hoist
to use it.
{Warning
An improperly stored spare tire
could come loose and cause a
crash. To avoid personal injury or
property damage, always store
the spare tire when the vehicle is
parked on a level surface. Store the tire under the rear of the
vehicle in the spare tire carrier.
1. Spare Tire (Valve Stem
Pointed Down)
2. Tire/Wheel Retainer
3. Hoist Cable
4. Hoist Assembly
5. Hoist Shaft
6. Jack Handle Extensions
7. Wheel Wrench
8. Spare Tire Lock (If Equipped)
9. Hoist Shaft Access Hole
10. Hoist End of Extension Tool

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 417
5. Insert the hoist end (10)through the hole (9) in the rear
bumper and onto the hoist
shaft.
Do not use the chiseled end of
the wheel wrench.
6. Raise the tire part way upward. Make sure the retainer is
seated in the wheel opening.
7. If equipped with a spare tirecable, orient the cable by
rotating the spare tire so that
the cable is by the frame
attachment location.
8. Raise the tire fully against the underside of the vehicle by
turning the wheel wrench
clockwise until you hear two
clicks or feel it skip twice. You
cannot overtighten the cable.9. Make sure the tire is storedsecurely. Push, pull, and then
try to turn the tire. If the tire
moves, use the wheel wrench
to tighten the cable.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
424 Vehicle Care
Towing the Vehicle
Caution
Incorrectly towing a disabled
vehicle may cause damage. The
damage would not be covered by
the vehicle warranty. Do not lash
or hook to suspension
components. Use the proper
straps around the tires to secure
the vehicle. Do not drag a locked
wheel/tire. Use tire skates or
dollies under any locked wheel/
tire while loading the vehicle. Do
not use a sling type lift to tow the
vehicle. This could damage the
vehicle.
Caution
If the vehicle cannot be shifted
into Neutral (N), do not use the
tow eye to tow the vehicle.
Vehicle damage may occur.GM recommends a flatbed tow truck
to transport a disabled vehicle. Use
ramps to help reduce approach
angles, if necessary. A towed
vehicle should have its drive wheels
off the ground. Contact Roadside
Assistance or a professional towing
service if the disabled vehicle must
be towed.
Front Attachment Points
1500
2500/3500
The vehicle is equipped with
specific attachment points to be
used to pull the vehicle onto a
flatbed car carrier from a flat road
surface. Do not use these
attachment points to pull the vehicle
from snow, mud or sand.
Recreational Vehicle
Towing
Recreational vehicle towing means
towing the vehicle behind another
vehicle, such as a motor home. The
two most common types of
recreational vehicle towing are

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
426 Vehicle Care
Two-wheel-drive vehicles and
vehicles with a single-speed transfer
case should not be towed with all
four wheels on the ground.
Dinghy Towing (Vehicles with a
Two-Speed Transfer Case)
Only dinghy tow four-wheel-drive
vehicles with a two-speed transfer
case that have an N (Neutral) and a
4
n(Four-Wheel Drive Low) setting.
{Warning
Shifting a four-wheel-drive
vehicle's transfer case into
N (Neutral) can allow the vehicle
to move even if the transmission
is in P (Park). You or others could
be injured. Set the parking brake
and use wheel blocks before
shifting the transfer case to
N (Neutral).
To dinghy tow: 1. Position the vehicle being towed behind the tow vehicle,
facing forward and on a level
surface.
2. Securely attach the vehicle being towed to the tow vehicle.
3. Start the engine.
4. Shift the transfer case to N (Neutral). See “Shifting into
N (Neutral)” underFour-Wheel
Drive 0227. 5. With the engine running,
release the parking brake and
verify that the transfer case is
in N (Neutral) by shifting the
transmission to D (Drive) and
then to R (Reverse). There
should be no movement while
shifting the transmission.
6. Shift the transmission to D (Drive).
7. If equipped with an ignition key, turn the ignition to ACC/
ACCESSORY. If equipped with
Keyless Access, turn the
engine off. Disregard the Shift
to P (Park) DIC message. See
Ignition Positions (Keyless
Access) 0208 or
Ignition Positions (Key Access)
0 210.
{Warning
To avoid death, serious injury,
or property damage, before
dinghy towing the vehicle, always
disconnect and secure the
(Continued)