2003 GMC YUKON heater

Some gasolines that are not reformulated for low
emissions may contain an octane-enhancing additive
called methylcyclopentadienyl manganese tricarbonyl
(MMT); ask the attendant where you buy gasoline
whether the fuel contains MMT. General Motors does not
recommend the use of such gasolines. Fuels containing
MMT can reduce the life of spark plugs and the
performance of the emission control system may be
affected. The malfunction indicator lamp may turn on. If
this occurs, return to your authorized GM dealer for
service.
Fuel E-85 (85% Ethanol)
The 8th digit of your vehicle identification number (VIN)
shows the code letter or number that identifies your
engine. You willfind the VIN at the top left of the
instrument panel. SeeVehicle Identification Number
(VIN) on page 5-96.
If your vehicle has the 5.3L V8 engine (VIN Code Z
only), you may use either regular unleaded gasoline or
ethanol fuel containing up to 85% ethanol (E-85);
also seeFuel on page 5-4. In all other engines, including
the 5.3L V8 (VIN Code T), use only regular unleaded
gasoline.Only vehicles that have the 5.3L V8 engine
(VIN Code Z) may use 85% ethanol fuel (E-85).
Many service stations will not have an 85% ethanol fuel
(E-85) pump available. The U. S. Department of
Energy has an alternative fuels website
(http://afdcmap.nrel.gov/nrel/) that can help youfind
E-85 fuel. Those stations that do have E-85 should have
a label indicating ethanol content. Do not use the fuel
if the ethanol content isgreaterthan 85%. Your vehicle
may not operate properly if the ethanol content is
greater than 85%.
At a minimum, E-85 should meet ASTM
Specification D 5798.
To insure quick starts in the wintertime, the E-85 fuel
must be formulated properly for your climate according
to ASTM specification D 5798. If you have trouble
starting on E-85, it may be because your E-85 fuel is
not properly formulated for your climate. If this happens,
switching to gasoline or adding gasoline to your fuel
tank may improve starting. Your vehicle is designed to
accommodate a mixture of gasoline and E-85 fuel.
For good starting and heater efficiency below 32°F
(0°C), the fuel mix in the fuel tank should contain no
more than 70% ethanol.
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2003 - Yukon/Yukon XL

Engine Coolant
The cooling system in your vehicle isfilled with
DEX-COOL®engine coolant. This coolant is designed
to remain in your vehicle for 5 years or 150,000 miles
(240 000 km), whichever occursfirst, if you add only
DEX-COOL
®extended life coolant.
The following explains your cooling system and how to
add coolant when it is low. If you have a problem
with engine overheating, seeEngine Overheating on
page 5-29.
A 50/50 mixture of clean, drinkable water and
DEX-COOL
®coolant will:
•Give freezing protection down to−34°F(−37°C).
•Give boiling protection up to 265°F (129°C).
•Protect against rust and corrosion.
•Help keep the proper engine temperature.
•Let the warning lights and gages work as they
should.Notice:When adding coolant, it is important that
you use only DEX-COOL
®(silicate-free) coolant.
If coolant other than DEX-COOL®is added to
the system, premature engine, heater core or
radiator corrosion may result. In addition, the engine
coolant will require change sooner—at 30,000 miles
(50,000 km) or 24 months, whichever occursrst.
Damage caused by the use of coolant other
than DEX-COOL
®is not covered by your new vehicle
warranty.
What to Use
Use a mixture of one-halfclean, drinkable waterand
one-half DEX-COOL®coolant which won’t damage
aluminum parts. If you use this coolant mixture,
you don’t need to add anything else.
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2003 - Yukon/Yukon XL

{CAUTION:
Adding only plain water to your cooling
system can be dangerous. Plain water, or
some other liquid such as alcohol, can boil
before the proper coolant mixture will. Your
vehicle’s coolant warning system is set for the
proper coolant mixture. With plain water or the
wrong mixture, your engine could get too hot
but you wouldn’t get the overheat warning.
Your engine could catchre and you or others
could be burned. Use a 50/50 mixture of clean,
drinkable water and DEX-COOL
®coolant.Notice:If you use an improper coolant mixture,
your engine could overheat and be badly damaged.
The repair cost wouldn’t be covered by your
warranty. Too much water in the mixture can freeze
and crack the engine, radiator, heater core and
other parts.
If you have to add coolant more than four times a year,
have your dealer check your cooling system.
Notice:If you use the proper coolant, you don’t
have to add extra inhibitors or additives which claim
to improve the system. These can be harmful.
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2003 - Yukon/Yukon XL

If No Steam Is Coming From Your
Engine
An overheat warning, along with a low coolant message,
can indicate a serious problem. SeeLow Coolant
underDIC Warnings and Messages on page 3-64.
If you get an engine overheat warning with no low
coolant message, but see or hear no steam, the problem
may not be too serious. Sometimes the engine can
get a little too hot when you:
•Climb a long hill on a hot day.
•Stop after high-speed driving.
•Idle for long periods in traffic.
•Tow a trailer. SeeTowing a Trailer on page 4-61.
If you get the overheat warning with no sign of steam, try
this for a minute or so:
1. In heavy traffic, let the engine idle in neutral while
stopped. If it is safe to do so, pull off the road. Shift
to park or neutral and let the engine idle.
2. Turn on your heater to full hot at the highest fan
speed and open the window as necessary.If you no longer have the overheat warning, you can
drive. Just to be safe, drive slower for about 10 minutes.
If the warning doesn’t come back on, you can drive
normally.
If the warning continues, pull over, stop, and park your
vehicle right away.
If there’s still no sign of steam, you can push down the
accelerator until the engine speed is about twice as
fast as normal idle speed for at least three minutes while
you’re parked. If you still have the warning,turn off
the engine and get everyone out of the vehicleuntil it
cools down. Also, seeOverheated Engine Protection
Operating Modelisted previously in this section.
You may decide not to lift the hood but to get service
help right away.
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2003 - Yukon/Yukon XL

The coolant level should
be at or above the FULL
COLD mark. If it isn’t,
you may have a leak at the
pressure cap or in the
radiator hoses, heater
hoses, radiator, water
pump or somewhere else
in the cooling system.
{CAUTION:
Heater and radiator hoses, and other engine
parts, can be very hot. Don’t touch them. If you
do, you can be burned.
Don’t run the engine if there is a leak. If you
run the engine, it could lose all coolant. That
could cause an enginere, and you could be
burned. Get any leakxed before you drive the
vehicle.If there seems to be no leak, start the engine again.
The engine cooling fan speed should increase when idle
speed is doubled by pushing the accelerator pedal
down. If it doesn’t, your vehicle needs service. Turn off
the engine.
Notice:Engine damage from running your engine
without coolant isn’t covered by your warranty.
See“Overheated Engine Protection Operating
Mode”in the Index for information on driving to a
safe place in an emergency.
Notice:When adding coolant, it is important that
you use only DEX-COOL
®(silicate-free) coolant.
If coolant other than DEX-COOL®is added to
the system, premature engine, heater core or
radiator corrosion may result. In addition, the engine
coolant will require change sooner—at 30,000 miles
(50 000 km) or 24 months, whichever occursrst.
Damage caused by the use of coolant other
than DEX-COOL
®is not covered by your new vehicle
warranty.
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2003 - Yukon/Yukon XL

{CAUTION:
Adding only plain water to your cooling
system can be dangerous. Plain water, or
some other liquid such as alcohol, can boil
before the proper coolant mixture will. Your
vehicle’s coolant warning system is set for the
proper coolant mixture. With plain water or the
wrong mixture, your engine could get too hot
but you wouldn’t get the overheat warning.
Your engine could catchre and you or others
could be burned. Use a 50/50 mixture of clean,
drinkable water and DEX-COOL
®coolant.
Notice:In cold weather, water can freeze and crack
the engine, radiator, heater core and other parts.
Use the recommended coolant and the proper
coolant mixture.
{CAUTION:
You can be burned if you spill coolant on hot
engine parts. Coolant contains ethylene glycol
and it will burn if the engine parts are hot
enough. Don’t spill coolant on a hot engine.
1. Park the vehicle on a
level surface. You can
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.
2. Turn the pressure cap slowly counterclockwise (left)
about one full turn. If you hear a hiss, wait for that to
stop. A hiss means there is still some pressure left.
3. Then keep turning the pressure cap slowly, and
remove it.
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2003 - Yukon/Yukon XL

Cleaning (cont.)
Underbody Maintenance...............................5-94
Video Screen............................................3-125
Weatherstrips..............................................5-91
Cleaning Aluminum or Chrome-Plated Wheels.....5-93
Cleaning Exterior Lamps/Lenses.......................5-92
Cleaning Fabric/Carpet....................................5-89
Cleaning Glass Surfaces..................................5-91
Cleaning Interior Plastic Components.................5-91
Cleaning Leather............................................5-90
Cleaning the Mirror.........................................2-43
Cleaning the Top of the Instrument Panel...........5-91
Cleaning the Windshield, Backglass and Wiper
Blades.......................................................5-93
Cleaning Tires................................................5-94
Cleaning Vinyl................................................5-90
Climate Control System...................................3-21
Dual ..........................................................3-22
Dual Automatic............................................3-26
Rear Air Conditioning and Heating System......3-33
Rear Air Conditioning and Heating System,
Electronic................................................3-35
Rear Air Conditioning System........................3-32
Compact Disc Messages................3-84, 3-97, 3-110
Compass Calibration...............................2-42, 2-44
Compass Operation.........................................2-44
Compass Variance..................................2-41, 2-44Content Theft-Deferrent....................................2-16
Control of a Vehicle.......................................... 4-6
Convenience Net............................................2-56
Coolant
Engine Temperature Gage............................3-46
Heater, Engine............................................2-21
Surge Tank Pressure Cap.............................5-29
Cooling System..............................................5-32
Cruise Control................................................3-11
Cruise Control Light........................................3-52
Cupholder(s)..................................................2-54
Current and Past Model Order Forms................7-11
Customer Assistance Information
Courtesy Transportation.................................. 7-7
Customer Assistance for Text Telephone (TTY)
Users....................................................... 7-4
Customer Assistance Offices........................... 7-4
Customer Satisfaction Procedure..................... 7-2
GM Mobility Program for Persons with
Disabilities................................................ 7-5
Reporting Safety Defects to General Motors....7-10
Reporting Safety Defects to the Canadian
Government............................................7-10
Reporting Safety Defects to the United States
Government.............................................. 7-9
Roadside Assistance Program......................... 7-5
Service Publications Ordering Information........7-10
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2003 - Yukon/Yukon XL

E
Easy Exit Seat...............................................2-60
Electrical System
Add-On Equipment......................................5-97
Fuses and Circuit Breakers...........................5-98
Power Windows and Other Power Options......5-97
Windshield Wiper Fuses...............................5-97
Electrochromic Mirror Operation................2-41, 2-43
Emissions Inspection and Maintenance
Programs...................................................3-50
Engine
Air Cleaner/Filter.........................................5-21
Battery.......................................................5-43
Check and Service Engine Soon Light............3-48
Compartment Overview................................5-12
Coolant......................................................5-26
Coolant Heater............................................2-21
Coolant Temperature Gage...........................3-46
Cooling System Inspection............................6-16
Exhaust.....................................................2-38
Fan Noise..................................................5-37
Oil .............................................................5-16
Overheating................................................5-29
Starting
......................................................2-20
ENGINE COOLANT HOT
.................................3-64
Engine Coolant Level Check
.............................6-11
Engine Hour Meter Display
...............................3-39Engine Oil Additives........................................5-19
Engine Oil Level Check...................................6-11
ENGINE OVERHEATED..................................3-65
Entering or Exiting the Third Row Seats.............. 1-8
Entertainment System
Cleaning the Video Screen..........................3-125
DVD Distortion..........................................3-123
Entry Lighting.................................................3-18
Environmental Concerns..................................4-26
Erasing HomeLink
®Buttons..............................2-53
Exit Lighting...................................................3-18
Express-Down Windows...................................2-15
Extender, Safety Belt.......................................1-43
Exterior Lamps...............................................3-14
F
Filter
Engine Air Cleaner......................................5-21
Finding a PTY Station
(RDS and XM™) .......................3-78, 3-88, 3-101
Finding a Station....................3-73, 3-76, 3-86, 3-99
Finish Care....................................................5-92
Finish Damage...............................................5-94
Fixed Mast Antenna.......................................3-125
Flash-To-Pass.................................................. 3-9
Flat Tire........................................................5-69
Flat Tire, Changing.........................................5-69
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2003 - Yukon/Yukon XL