2018 GMC SIERRA DENALI maintenance

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
244 Driving and Operating After Off-Road Driving Remove any brush or debris that
has collected on the underbody or
chassis, or under the hood. These
accumulations can be a fire hazard.
After operation in mud or sand,
have the brake linings cleaned and
checked. These substances can
cause glazing and uneven braking.
Check the body structure, driveline,
steering, suspension, wheels, tires,
and exhaust system for damage and
check the fuel lines and cooling
system for any leakage.
More frequent maintenance service
is required. See the Maintenance
Schedule 0 448 .
Driving on Wet Roads Rain and wet roads can reduce
vehicle traction and affect your
ability to stop and accelerate.
Always drive slower in these types
of driving conditions and avoid
driving through large puddles and
deep-standing or flowing water. { WarningWet brakes can cause crashes.
They might not work as well in a
quick stop and could cause
pulling to one side. You could
lose control of the vehicle.
After driving through a large
puddle of water or a car/vehicle
wash, lightly apply the brake
pedal until the brakes work
normally.
Flowing or rushing water creates
strong forces. Driving through
flowing water could cause the
vehicle to be carried away. If this
happens, you and other vehicle
occupants could drown. Do not
ignore police warnings and be
very cautious about trying to drive
through flowing water. Hydroplaning Hydroplaning is dangerous. Water
can build up under the vehicle's
tires so they actually ride on the
water. This can happen if the road is
wet enough and you are going fast
enough. When the vehicle is
hydroplaning, it has little or no
contact with the road.
There is no hard and fast rule about
hydroplaning. The best advice is to
slow down when the road is wet.
Other Rainy Weather Tips Besides slowing down, other wet
weather driving tips include:
.
Allow extra following distance.
.
Pass with caution.
.
Keep windshield wiping
equipment in good shape.
.
Keep the windshield washer fluid
reservoir filled.
.
Have good tires with proper
tread depth. See Tires 0 389 .
.
Turn off cruise control.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 307Maintenance when Trailer
Towing The vehicle needs service more
often when pulling a trailer. See
Maintenance Schedule 0 448 .
Things that are especially important
in trailer operation are automatic
transmission fluid, engine oil, axle
lubricant, belts, cooling system, and
brake system. It is a good idea to
inspect these before and during
the trip.
Check periodically to see that all
hitch nuts and bolts are tight.
Engine Cooling When Trailer
Towing The cooling system may temporarily
overheat during severe operating
conditions. See Engine Overheating
0 363 . Trailer Towing If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
Do not tow a trailer during break-in.
See New Vehicle Break-In 0 255 .
{ WarningThe driver can lose control when
pulling 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.
The driver and passengers could
be seriously injured. The vehicle
may also be damaged; the
resulting 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. CautionPulling a trailer improperly can
damage the vehicle and result in
costly repairs not covered by the
vehicle warranty. To pull a trailer
correctly, follow the advice in this
section and see your dealer for
important information about
towing a trailer with the vehicle.
See Vehicle Load Limits 0 248 for
more information about the vehicle's
maximum load capacity.
To identify the trailering capacity of
the vehicle, read the information in
“ Weight of the Trailer ” later in this
section.
Trailering is different than just
driving the vehicle by itself.
Trailering means changes in
handling, acceleration, braking,
durability, and fuel economy.
Successful, safe trailering takes
correct equipment, and it has to be
used properly.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
336 Driving and Operating Warning (Continued) (20-25 mph) and fully apply
the manual trailer brake
apply lever. Also check that
the trailer brake lamps and
other lamps are functioning
correctly.
.
If the trailer brakes are not
operating properly at any
time, or if a DIC message
indicates problems with the
trailer connections or trailer
brakes, carefully pull the
vehicle over to the side of
the road when traffic
conditions allow. Conversions and
Add-Ons Add-On Electrical
Equipment
{ WarningThe Data Link Connector (DLC) is
used for vehicle service
and Emission Inspection/
Maintenance testing. See
Malfunction Indicator Lamp
(Check Engine Light) 0 150 .
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. CautionSome electrical equipment can
damage the vehicle or cause
components to not work and
would not be covered by the
vehicle warranty. Always check
with your dealer before adding
electrical equipment.
Add-on equipment can drain the
vehicle's 12-volt battery, even if the
vehicle is not operating.
The vehicle has an airbag system.
Before attempting to add anything
electrical to the vehicle, see
Servicing the Airbag-Equipped
Vehicle 0 90 and Adding Equipment
to the Airbag-Equipped Vehicle
0 90 .
For information on wiring auxiliary
switches, see www.gmupfitter.com
or contact your dealer.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
344 Vehicle Care
Vehicle Checks Doing Your Own
Service Work
{ WarningIt can be dangerous to work on
your vehicle if you do not have
the proper knowledge, service
manual, tools, or parts. Always
follow owner ’ s manual procedures
and consult the service manual
for your vehicle before doing any
service work.
If doing some of your own service
work, use the proper service
manual. It tells you much more
about how to service the vehicle
than this manual can. To order the
proper service manual, see Service
Publications Ordering Information
0 474 .
This vehicle has an airbag system.
Before attempting to do your own
service work, see Servicing the
Airbag-Equipped Vehicle 0 90 . Keep a record with all parts receipts
and list the mileage and the date of
any service work performed. See
Maintenance Records 0 459 .
CautionEven small amounts of
contamination can cause damage
to vehicle systems. Do not allow
contaminants to contact the fluids,
reservoir caps, or dipsticks.
Hood To open the hood:
1. Pull the handle with this symbol
on it. It is inside the vehicle
under the steering wheel. 2. Go to the front of the vehicle to
find the secondary hood
release. The handle is under
the front edge of the hood near
the center. Push the handle to
the right and at the same time
raise the hood.
Before closing the hood, be sure all
the filler caps are on properly. Then
bring the hood from full open to
within 15 cm (6 in) from the closed
position, pause, and push the front
center of the hood with a swift, firm
motion to fully close the hood.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Vehicle Care 355Caution (Continued)automatic transmission fluid listed
in Recommended Fluids and
Lubricants 0 456 .
Change the fluid and filter at the
scheduled maintenance intervals
listed in Maintenance Schedule
0 448 . Be sure to use the
transmission fluid listed in
Recommended Fluids and
Lubricants 0 456 .
How to Check Automatic
Transmission Fluid
Caution
Too much or too little fluid can
damage the transmission. Too
much can mean that some of the
fluid could come out and fall on
hot engine parts or exhaust
system parts, starting a fire. Too
little fluid could cause the
(Continued) Caution (Continued) transmission to overheat. Be sure
to get an accurate reading if
checking the transmission fluid.
Before checking the fluid level,
prepare the vehicle:
1. Start the engine and park the
vehicle on a level surface.
Keep the engine running.
2. Apply the parking brake and
place the shift lever in P (Park).
3. With your foot on the brake
pedal, move the shift lever
through each gear range,
pausing for about
three seconds in each range.
Then, move the shift lever back
to P (Park).
4. Allow the engine to idle (500 –
800 rpm) for at least
one minute. Slowly release the
brake pedal. 5. Keep the engine running and
check the transmission fluid
temperature on the Driver
Information Center (DIC).
See Driver Information Center
(DIC) (Uplevel and Denali
Cluster) 0 160 or Driver
Information Center (DIC) (Base
Level Cluster) 0 158 .
6. Using the transmission fluid
temperature reading, determine
and perform the appropriate
check procedure. If the
transmission fluid temperature
reading is not within the
required temperature ranges,
allow the vehicle to cool,
or operate the vehicle until the
appropriate transmission fluid
temperature is reached.
Cold Check Procedure
Use this procedure only as a
reference to determine if the
transmission has enough fluid to be
operated safely until a hot check
procedure can be made. The hot
check procedure is the most
accurate method to check the fluid
level. Perform the hot check

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
358 Vehicle Care CautionUse of the incorrect automatic
transmission fluid may damage
the vehicle, and the damage may
not be covered by the vehicle
warranty. Always use the
automatic transmission fluid listed
in Recommended Fluids and
Lubricants 0 456 .
Change the fluid and filter at the
scheduled maintenance intervals
listed in Maintenance Schedule
0 448 . Be sure to use the
transmission fluid listed in
Recommended Fluids and
Lubricants 0 456 .
Engine Air Cleaner/Filter If the vehicle has a diesel engine,
see “ 8-Cylinder Pickup Models ”
under “ Engine Air Cleaner/Filter ” in
the Duramax diesel supplement for
the correct inspection and
replacement procedures. The engine air cleaner/filter is on
the passenger side of the engine
compartment. See Engine
Compartment Overview 0 345 .
When to Inspect the Engine Air
Cleaner/Filter For intervals on changing and
inspecting the engine air filter, see
Maintenance Schedule 0 448 .
How to Inspect the Engine Air
Cleaner/Filter Do not start the engine or have the
engine running with the engine air
cleaner/filter housing open. Before
removing the engine air cleaner/
filter, make sure that the engine air
cleaner/filter housing and nearby
components are free of dirt and
debris. Remove the engine air
cleaner/filter. Lightly tap and shake
the engine air cleaner/filter (away
from the vehicle), to release loose
dust and dirt. Inspect the engine air
cleaner/filter for damage, and
replace if damaged. Do not clean
the engine air cleaner/filter or
components with water or
compressed air. To inspect or replace the engine air
cleaner/filter:
1. Screws
2. Electrical Connectors
3. Air Duct Clamp
1. Locate the air cleaner/filter
assembly. See Engine
Compartment Overview 0 345 .
2. Disconnect the outlet duct by
loosening the air duct
clamp (3).
3. Disconnect the electrical
connectors (2) and the
connector harness from the
cover.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
368 Vehicle Care Replacing Brake System Parts Always replace brake system parts
with new, approved replacement
parts. If this is not done, the brakes
may not work properly. The braking
performance expected can change
in many other ways if the wrong
replacement brake parts are
installed or parts are improperly
installed.
Brake Fluid
The brake master cylinder reservoir
is filled with DOT 3 brake fluid. See
Engine Compartment Overview
0 345 for the location of the
reservoir.
There are only two reasons why the
brake fluid level in the reservoir may
go down: .
Normal brake lining wear. When
new linings are installed, the
fluid level goes back up.
.
A fluid leak in the brake
hydraulic system. Have the
brake hydraulic system fixed.
With a leak, the brakes will not
work well.
Always clean the brake fluid
reservoir cap and the area around
the cap before removing it.
Do not top off the brake fluid.
Adding fluid does not correct a leak.
If fluid is added when the linings are
worn, there will be too much fluid
when new brake linings are
installed. Add or remove fluid, as
necessary, only when work is done
on the brake hydraulic system.
{ Warning
If too much brake fluid is added, it
can spill on the engine and burn,
if the engine is hot enough. You
or others could be burned, and
the vehicle could be damaged.
(Continued) Warning (Continued) Add brake fluid only when work is
done on the brake hydraulic
system.
When the brake fluid falls to a low
level, the brake warning light comes
on. See Brake System Warning
Light 0 152 .
Brake fluid absorbs water over time.
Replace brake fluid at the specified
intervals to prevent increased
stopping distance. See Maintenance
Schedule 0 448 .
Checking Brake Fluid Check brake fluid by looking at the
brake fluid reservoir. See Engine
Compartment Overview 0 345 .

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Vehicle Care 369
The fluid level should be above
MIN. If it is not, have the brake
hydraulic system checked to see if
there is a leak.
After work is done on the brake
hydraulic system, make sure the
level is above MIN but not over the
MAX mark.
What to Add
Use only GM approved DOT 3
brake fluid from a clean, sealed
container. See Recommended
Fluids and Lubricants 0 456 .{ WarningThe wrong or contaminated brake
fluid could result in damage to the
brake system. This could result in
the loss of braking leading to a
possible injury. Always use the
proper GM approved brake fluid.
CautionIf brake fluid is spilled on the
vehicle's painted surfaces, the
paint finish can be damaged.
Immediately wash off any painted
surface.
Battery - North America The original equipment battery is
maintenance free. Do not remove
the cap and do not add fluid.
Refer to the replacement number
shown on the original battery label
when a new battery is needed. See
Engine Compartment Overview
0 345 for battery location.{ WarningWARNING: Battery posts,
terminals, and related
accessories contain lead and lead
compounds, chemicals known to
the State of California to cause
cancer and birth defects or other
reproductive harm. Batteries also
contain other chemicals known to
the State of California to cause
cancer. WASH HANDS AFTER
HANDLING. For more information
go to www.P65Warnings.ca.gov/
passenger-vehicle.
See California Proposition
65 Warning 0 343 and the back
cover.
Vehicle Storage
{ Warning
Batteries have acid that can burn
you and gas that can explode.
You can be badly hurt if you are
(Continued)