Transmission service GMC YUKON 2018 Owner's Manual

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - CRC - 11/3/17
Instruments and Controls 143
Caution
Do not drive the vehicle while the
transmission fluid is overheating,
or the transmission can be
damaged. This could lead to
costly repairs that would not be
covered by the warranty.
Voltmeter Gauge
Standard Theme
When the ignition is on, this gauge
indicates the battery voltage. When the engine is running, this
gauge shows the condition of the
charging system. The gauge can
transition from a higher to lower or a
lower to higher reading. This is
normal. If the vehicle is operating
outside the normal operating range,
the charging system light comes on.
See
Charging System Light 0145
for more information. The voltmeter
gauge may also read lower when in
fuel economy mode. This is normal.
Readings outside the normal
operating range can also occur
when a large number of electrical
accessories are operating in the
vehicle and the engine is left idling
for an extended period. This
condition is normal since the
charging system is not able to
provide full power at engine idle. As
engine speeds are increased, this
condition should correct itself as
higher engine speeds allow the
charging system to create maximum
power.
The vehicle can only be driven for a
short time with the readings outside
the normal operating range. If the vehicle must be driven, turn off all
accessories, such as the radio and
air conditioner and unplug all
chargers and accessories.
Readings outside the normal
operating range indicate a possible
problem in the electrical system.
Have the vehicle serviced as soon
as possible.
Seat Belt Reminders
Driver Seat Belt Reminder
Light
There is a driver seat belt reminder
light on the instrument cluster.
When the vehicle is started, this
light flashes and a chime may come
on to remind the driver to fasten
their seat belt. Then the light stays
on solid until the belt is buckled.
This cycle may continue several

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - CRC - 11/3/17
146 Instruments and Controls
system. Have it checked by your
dealer. Driving while this light is on
could drain the battery.
When this light comes on, or is
flashing, the Driver Information
Center (DIC) also displays a
message.
If a short distance must be driven
with the light on, be sure to turn off
all accessories, such as the radio
and air conditioner.
Malfunction Indicator
Lamp (Check Engine
Light)
This light is part of the vehicle’s
emission control on-board
diagnostic system. If this light is on
while the engine is running, a
malfunction has been detected and
the vehicle may require service. The
light should come on to show that it
is working when the ignition is in
Service Mode. SeeIgnition
Positions (Key Access) 0212 or
Ignition Positions (Keyless Access)
0 210.
Malfunctions are often indicated by
the system before any problem is
noticeable. Being aware of the light
and seeking service promptly when
it comes on may prevent damage.
Caution
If the vehicle is driven continually
with this light on, the emission
control system may not work as
well, the fuel economy may be
lower, and the vehicle may not
run smoothly. This could lead to
costly repairs that might not be
covered by the vehicle warranty.
Caution
Modifications to the engine,
transmission, exhaust, intake,
or fuel system, or the use of
replacement tires that do not
meet the original tire
specifications, can cause this light
to come on. This could lead to
costly repairs not covered by the
vehicle warranty. This could also
affect the vehicle’s ability to pass
an Emissions Inspection/
Maintenance test. See
Accessories and Modifications
0282.
If the light is flashing : A
malfunction has been detected that
could damage the emission control
system and increase vehicle
emissions. Diagnosis and service
may be required.
To help prevent damage, reduce
vehicle speed and avoid hard
accelerations and uphill grades.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - CRC - 11/3/17
Instruments and Controls 161
HUD Troubleshooting
Check that:
.Nothing is covering the
HUD lens.
. HUD brightness setting is not
too dim or too bright.
. HUD is adjusted to the proper
height.
. Polarized sunglasses are
not worn.
. Windshield and HUD lens are
clean.
If the HUD image is not correct,
contact your dealer.
The windshield is part of the HUD
system. See Windshield
Replacement 0309.
Vehicle Messages
Messages displayed on the DIC
indicate the status of the vehicle or
some action that may be needed to
correct a condition. Multiple
messages may appear one after
another.
The messages that do not require
immediate action can be
acknowledged and cleared by
pressing
V. The messages that
require immediate action cannot be
cleared until that action is
performed.
All messages should be taken
seriously; clearing the message
does not correct the problem.
If a SERVICE message appears,
see your dealer.
Follow the instructions given in the
messages. The system displays
messages regarding the following
topics:
. Service Messages
. Fluid Levels
. Vehicle Security .
Brakes
. Ride Control Systems
. Driver Assistance Systems
. Cruise Control
. Lighting and Bulb Replacement
. Wiper/Washer Systems
. Doors and Windows
. Seat Belts
. Airbag Systems
. Engine and Transmission
. Tire Pressure
. Battery
Engine Power Messages
ENGINE POWER IS REDUCED
This message displays when the
vehicle's propulsion power is
reduced. Reduced propulsion power
can affect the vehicle's ability to
accelerate. If this message is on,
but there is no observed reduction
in performance, proceed to your
destination. The performance may
be reduced the next time the vehicle

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - CRC - 11/3/17
202 Driving and Operating
Hill and Mountain Roads
Driving on steep hills or through
mountains is different than driving
on flat or rolling terrain. Tips include:
.Keep the vehicle serviced and in
good shape.
. Check all fluid levels and brakes,
tires, cooling system, and
transmission.
. Shift to a lower gear when going
down steep or long hills.
{Warning
Using the brakes to slow the
vehicle on a long downhill slope
can cause brake overheating, can
reduce brake performance, and
could result in a loss of braking.
Shift the transmission to a lower
gear to let the engine assist the
brakes on a steep downhill slope.
{Warning
Coasting downhill in N (Neutral)
or with the ignition off is
dangerous. This can cause
overheating of the brakes and
loss of steering assist. Always
have the engine running and the
vehicle in gear.
. Drive at speeds that keep the
vehicle in its own lane. Do not
swing wide or cross the
center line.
. Be alert on top of hills;
something could be in your lane
(e.g., stalled car, accident).
. Pay attention to special road
signs (e.g., falling rocks area,
winding roads, long grades,
passing or no-passing zones)
and take appropriate action.
Winter Driving
Driving on Snow or Ice
Snow or ice between the tires and
the road creates less traction or
grip, so drive carefully. Wet ice can
occur at about 0 °C (32 °F) when
freezing rain begins to fall. Avoid
driving on wet ice or in freezing rain
until roads can be treated.
For Slippery Road Driving:
.Accelerate gently. Accelerating
too quickly causes the wheels to
spin and makes the surface
under the tires slick.
. Turn on Traction Control. See
Traction Control/Electronic
Stability Control 0234.
. The Antilock Brake System
(ABS) improves vehicle stability
during hard stops, but the
brakes should be applied sooner
than when on dry pavement.
See Antilock Brake System
(ABS) 0231.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - CRC - 11/3/17
Driving and Operating 211
If the vehicle must be shut off in an
emergency:1. Brake using a firm and steady pressure. Do not pump the
brakes repeatedly. This may
deplete power assist, requiring
increased brake pedal force.
2. Shift the vehicle to N (Neutral). This can be done while the
vehicle is moving. After shifting
to N (Neutral), firmly apply the
brakes and steer the vehicle to
a safe location.
3. Come to a complete stop, shift to P (Park), and turn the
ignition off. On vehicles with an
automatic transmission, the
shift lever must be in P (Park)
to turn the ignition off.
4. Set the parking brake. See Parking Brake 0232.{Warning
Turning off the vehicle while
moving may cause loss of power
assist in the brake and steering
systems and disable the airbags.
While driving, only shut the
vehicle off in an emergency.
If the vehicle cannot be pulled over,
and must be shut off while driving,
press and hold ENGINE START/
STOP for longer than two seconds,
or press twice in five seconds.
ACC/ACCESSORY (Amber
Indicator Light) : This mode allows
some electrical accessories to be
used when the engine is off.
With the ignition off, pressing the
button one time without the brake
pedal applied will place the ignition
system in ACC/ACCESSORY.
The ignition will switch from ACC/
ACCESSORY to off after
five minutes to prevent battery
rundown. ON/RUN/START (Green Indicator
Light) :
This mode is for driving and
starting. With the ignition off, and
the brake pedal applied, pressing
the button once will turn the ignition
on. Once engine cranking begins,
release the button. Engine cranking
will continue until the engine starts.
See Starting the Engine 0213.
Service Mode
This power mode is available for
service and diagnostics, and to
verify the proper operation of the
malfunction indicator lamp as may
be required for emission inspection
purposes. With the vehicle off, and
the brake pedal not applied,
pressing and holding the button for
more than five seconds will place
the vehicle in Service Mode. The
instruments and audio systems will
operate as they do when the ignition
is on, but the vehicle will not be able
to be driven. The engine will not
start in Service Mode. Press the
button again to turn the ignition off.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - CRC - 11/3/17
212 Driving and Operating
Ignition Positions (Key
Access)
Vehicles with Key Access have an
ignition switch with four different
positions.
To shift out of P (Park), the ignition
must be on or in ACC/ACCESSORY
and the regular brake pedal must be
applied.
0 (STOPPING THE ENGINE/LOCK/
OFF) :When the vehicle is stopped,
turn the ignition switch to LOCK/
OFF to turn the engine off. Retained Accessory Power (RAP) will remain
active. See
Retained Accessory
Power (RAP) 0216.
This position locks the ignition and
steering wheel. It also locks the
transmission on automatic
transmission vehicles. The key can
be removed in LOCK/OFF.
The steering can bind with the
wheels turned off center. If this
happens, move the steering wheel
from right to left while turning the
key to ACC/ACCESSORY. If this
does not work, then the vehicle
needs service.
Do not turn the engine off when the
vehicle is moving. This will cause a
loss of power assist in the brake
and steering systems and disable
the airbags.
If the vehicle must be shut off in an
emergency: 1. Brake using a firm and steady pressure. Do not pump the
brakes repeatedly. This may
deplete power assist, requiring
increased brake pedal force. 2. Shift the vehicle to N (Neutral).
This can be done while the
vehicle is moving. After shifting
to N (Neutral), firmly apply the
brakes and steer the vehicle to
a safe location.
3. Come to a complete stop, shift to P (Park), and turn the
ignition to LOCK/OFF. On
vehicles with an automatic
transmission, the shift lever
must be in P (Park) to turn the
ignition switch to the LOCK/
OFF position.
4. Set the parking brake. See Parking Brake 0232.
{Warning
Turning off the vehicle while
moving may cause loss of power
assist in the brake and steering
systems and disable the airbags.
While driving, only shut the
vehicle off in an emergency.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - CRC - 11/3/17
Driving and Operating 213
If the vehicle cannot be pulled over,
and must be shut off while driving,
turn the ignition to ACC/
ACCESSORY.
Caution
Using a tool to force the key to
turn in the ignition could cause
damage to the switch or break the
key. Use the correct key, make
sure it is all the way in, and turn it
only with your hand. If the key
cannot be turned by hand, see
your dealer.
1 (ACC/ACCESSORY) : This
position lets things like the radio
and the windshield wipers operate
while the engine is off. It also
unlocks the steering wheel. Use this
position if the vehicle must be
pushed or towed.
2 (ON/RUN) : This position can be
used to operate the electrical
accessories and to display some
instrument cluster warning and
indicator lights. This position can
also be used for service and diagnostics, and to verify the proper
operation of the malfunction
indicator lamp as may be required
for emission inspection purposes.
The switch stays in this position
when the engine is running. The
transmission is also unlocked in this
position on automatic transmission
vehicles.
If the key is left in the ACC/
ACCESSORY or ON/RUN position
with the engine off, the battery could
be drained. The vehicle may not
start if the battery is allowed to drain
for an extended period of time.
3 (START) :
This is the position that
starts the engine. When the engine
starts, release the key. The ignition
switch returns to ON/RUN for
driving.
A warning tone will sound when the
driver door is opened and the
ignition is in ACC/ACCESSORY or
LOCK/OFF, and the key is in the
ignition.
Starting the Engine
Move the shift lever to P (Park) or
N (Neutral). The engine will not start
in any other position. To restart the
engine when the vehicle is already
moving, use N (Neutral) only.
Caution
Do not try to shift to P (Park) if the
vehicle is moving. If you do, you
could damage the transmission.
Shift to P (Park) only when the
vehicle is stopped.
Caution
If you add electrical parts or
accessories, you could change
the way the engine operates. Any
resulting damage would not be
covered by the vehicle warranty.
See Add-On Electrical Equipment
0 279.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - CRC - 11/3/17
218 Driving and Operating
to pull the shift lever out of P (Park).
This is called torque lock. To
prevent torque lock, set the parking
brake and then shift into P (Park)
properly before you leave the
driver seat.
When you are ready to drive, move
the shift lever out of P (Park) before
you release the parking brake.
If torque lock does occur, you may
need to have another vehicle push
yours a little uphill to take some of
the pressure from the parking pawl
in the transmission. You will then be
able to pull the shift lever out of
P (Park).
Shifting out of Park
This vehicle is equipped with an
electronic shift lock release system.
The shift lock release system is
designed to prevent movement of
the shift lever out of P (Park), unless
the ignition is on and the brake
pedal is applied.The shift lock release is always
functional except in the case of an
uncharged or low voltage (less than
9 volt) battery.
If the vehicle has an uncharged
battery or a battery with low voltage,
try charging or jump starting the
battery. See
Jump Starting - North
America 0356.
To shift out of P (Park): 1. Apply the brake pedal.
2. Move the shift lever to the desired position.
If you still are unable to shift out of
P (Park): 1. Ease the pressure on the shift lever.
2. While holding down the brake pedal, push the shift lever all
the way into P (Park).
3. Move the shift lever to the desired position.
If you are still having a problem
shifting, then have the vehicle
serviced soon.
Parking over Things
That Burn
{Warning
Things that can burn could touch
hot exhaust parts under the
vehicle and ignite. Do not park
over papers, leaves, dry grass,
or other things that can burn.
Active Fuel Management
Vehicles with V8 engines may have
Active Fuel Management. This
system allows the engine to operate
on either all or half of its cylinders,
depending on the driving conditions.
When less power is required, such
as cruising at a constant vehicle
speed, the system will operate in
the half cylinder mode, allowing the
vehicle to achieve better fuel
economy. When greater power
demands are required, such as
accelerating from a stop, passing,

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - CRC - 11/3/17
266 Driving and Operating
altitude on steep uphill grades, the
vehicle may show signs similar to
engine overheating. To avoid this,
let the engine run while parked,
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, seeEngine Overheating 0298.
Parking on Hills
{Warning
Parking the vehicle on a hill with
the trailer attached can be
dangerous. If something goes
wrong, the rig could start to move.
People can be injured, and both
the vehicle and the trailer can be
damaged. When possible, always
park the rig on a flat surface.
If parking the rig on a hill: 1. Press the brake pedal, but do not shift into P (Park) yet. Turn
the wheels into the curb if
facing downhill or into traffic if
facing uphill. 2. Have someone place chocks
under the trailer wheels.
3. When the wheel chocks are in place, release the regular
brakes until the chocks absorb
the load.
4. Reapply the brake pedal. Then apply the parking brake and
shift into P (Park).
5. Release the brake pedal.
Leaving After Parking on a Hill
1. Apply and hold the brake pedal.
2. Start the engine.
3. Shift into a gear.
4. Release the parking brake.
5. Let up on the brake pedal.
6. Drive slowly until the trailer is clear of the chocks.
7. Stop and have someone pick up and store the chocks.
Maintenance when Trailer
Towing
The vehicle needs service more
often when pulling a trailer. See
Maintenance Schedule 0376.
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.
Trailer Towing
Do not tow a trailer during break-in.
See New Vehicle Break-In 0209.
Before towing a trailer, see
"Hands-Free Operation" under
Liftgate 045.

GMC Yukon/Yukon XL/Denali Owner Manual (GMNA-Localizing-U.S./
Canada/Mexico-11349262) - 2018 - CRC - 11/3/17
280 Vehicle Care
Vehicle Care
General Information
General Information . . . . . . . . . . 281
California Proposition65 Warning . . . . . . . . . . . . . . . . . 281
California Perchlorate Materials Requirements . . . . . 282
Accessories and Modifications . . . . . . . . . . . . . . . . 282
Vehicle Checks
Doing Your OwnService Work . . . . . . . . . . . . . . . 282
Hood . . . . . . . . . . . . . . . . . . . . . . . . . 283
Engine Compartment Overview . . . . . . . . . . . . . . . . . . . . 284
Engine Oil . . . . . . . . . . . . . . . . . . . . 287
Engine Oil Life System . . . . . . . 289
Automatic Transmission Fluid (6 Speed Transmission) . . . . . 290
Automatic Transmission Fluid (8 and 10 Speed
Transmission) . . . . . . . . . . . . . . . 293
Engine Air Cleaner/Filter . . . . . . 294
Cooling System . . . . . . . . . . . . . . 295
Engine Overheating . . . . . . . . . . 298
Engine Fan . . . . . . . . . . . . . . . . . . . 300
Washer Fluid . . . . . . . . . . . . . . . . . 300 Brakes . . . . . . . . . . . . . . . . . . . . . . . 301
Brake Fluid . . . . . . . . . . . . . . . . . . . 302
Battery - North America . . . . . . 303
Four-Wheel Drive . . . . . . . . . . . . . 303
Front Axle . . . . . . . . . . . . . . . . . . . . 304
Rear Axle . . . . . . . . . . . . . . . . . . . . 305
Noise Control System . . . . . . . . 305
Starter Switch Check . . . . . . . . . 306
Automatic Transmission Shift
Lock Control Function
Check . . . . . . . . . . . . . . . . . . . . . . . 307
Ignition Transmission Lock Check . . . . . . . . . . . . . . . . . . . . . . . 307
Park Brake and P (Park) Mechanism Check . . . . . . . . . . 307
Wiper Blade Replacement . . . . 308
Glass Replacement . . . . . . . . . . 309
Windshield Replacement . . . . . 309
Gas Strut(s) . . . . . . . . . . . . . . . . . . 309
Headlamp Aiming
Headlamp Aiming . . . . . . . . . . . . 310
Bulb Replacement
Bulb Replacement . . . . . . . . . . . . 311
High Intensity Discharge (HID) Lighting . . . . . . . . . . . . . . . . . . . . . 311
LED Lighting . . . . . . . . . . . . . . . . . . 311
Fog Lamps . . . . . . . . . . . . . . . . . . . 311
Back-Up Lamps . . . . . . . . . . . . . . 311
License Plate Lamp . . . . . . . . . . 312
Electrical System
Electrical System Overload . . . 313
Fuses and Circuit Breakers . . . 313
Engine Compartment Fuse Block . . . . . . . . . . . . . . . . . . . . . . . . 314
Instrument Panel Fuse
Block (Left) . . . . . . . . . . . . . . . . . 318
Instrument Panel Fuse Block (Right) . . . . . . . . . . . . . . . . . . . . . . 321
Rear Compartment Fuse Block . . . . . . . . . . . . . . . . . . . . . . . . 323
Wheels and Tires
Tires . . . . . . . . . . . . . . . . . . . . . . . . . . 324
All-Season Tires . . . . . . . . . . . . . . 325
Winter Tires . . . . . . . . . . . . . . . . . . 325
Low-Profile Tires . . . . . . . . . . . . . 326
All-Terrain Tires . . . . . . . . . . . . . . . 326
Tire Sidewall Labeling . . . . . . . . 326
Tire Designations . . . . . . . . . . . . . 327
Tire Terminology andDefinitions . . . . . . . . . . . . . . . . . . 328
Tire Pressure . . . . . . . . . . . . . . . . . 331
Tire Pressure for High-Speed Operation . . . . . . . . . . . . . . . . . . . 332
Tire Pressure Monitor System . . . . . . . . . . . . . . . . . . . . . . 333
Tire Pressure Monitor Operation . . . . . . . . . . . . . . . . . . . 334
Tire Inspection . . . . . . . . . . . . . . . . 337