2002 GMC YUKON XL DENALI engine

4-51 Driving with a Trailer
CAUTION:
If you have a rear-most window open and you
pull a trailer with your vehicle, carbon monoxide
(CO) could come into your vehicle. You can't see
or smell CO. It can cause unconsciousness or
death. See ªEngine Exhaustº in the Index. To
maximize your safety when towing a trailer:

Have your exhaust system inspected for
leaks, and make necessary repairs before
starting on your trip.

Keep the rear
-most windows closed.

If exhaust does come into your vehicle
through a window in the rear or another
opening, drive with your front, main
heating or cooling system on and with the
fan on any speed. This will bring fresh,
outside air into your vehicle. Do not use
recirculation because it only recirculates
the air inside your vehicle. See ªComfort
Controlsº in the Index.
Towing a trailer requires a certain amount of experience.
Before setting out for the open road, you'll want to get
to know your rig. Acquaint yourself with the feel of
handling and braking with the added weight of the
trailer. And always keep in mind that the vehicle you are
driving is now a good deal longer and not nearly as
responsive as your vehicle is by itself.
Before you start, check the trailer hitch and platform
(and attachments), safety chains, electrical connector,
lamps, tires and mirror adjustment. If the trailer has
electric brakes, start your vehicle and trailer moving and
then apply the trailer brake controller by hand to be sure
the brakes are working. This lets you check your
electrical connection at the same time.
During your trip, check occasionally to be sure that the
load is secure, and that the lamps and any trailer brakes
are still working.

4-53 Driving On Grades
Reduce speed and shift to a lower gear before you start
down a long or steep downgrade. If you don't shift
down, you might have to use your brakes so much that
they would get hot and no longer work well.
You can tow in DRIVE (D). You may want to shift the
transmission to THIRD (3) or, if necessary, a lower gear
selection if the transmission shifts too often (e.g., under
heavy loads and/or hilly conditions).
You may also want to activate the tow/haul mode if the
transmission shifts too often. See ªTow/Haul Modeº in
the Index.
When towing at high altitude on steep uphill grades,
consider the following: Engine coolant will boil at a
lower temperature than at normal altitudes. If you turn
your engine off immediately after towing at high altitude
on steep uphill grades, your vehicle may show signs
similar to engine overheating. To avoid this, let the
engine run while parked (preferably on level ground)
with the automatic transmission in PARK (P) for a
few minutes before turning the engine off. If you do
get the overheat warning, see ªEngine Overheatingº
in the Index.
Parking on Hills
CAUTION:
You really should not park your vehicle, with a
trailer attached, on a hill. If something goes
wrong, your rig could start to move. People can
be injured, and both your vehicle and the trailer
can be damaged.
But if you ever have to park your rig on a hill, here's
how to do it:
1. Apply your regular brakes, but don't shift into
PARK (P) yet.
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 regular brakes. Then apply your parking
brake and shift into PARK (P).
5. Release the regular brakes.

4-54 When You Are Ready to Leave After
Parking on a Hill
1. Apply your regular brakes and hold the pedal down
while you:

start your engine,

shift into a gear, and

release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the chocks.
Maintenance When Trailer Towing
Your vehicle will need service more often when you're
pulling a trailer. See the Maintenance Schedule for more
on this. Things that are especially important in trailer
operation are automatic transmission fluid (don't
overfill), engine oil, axle lubricant, belt, cooling system
and brake system. Each of these is covered in this
manual, and the Index will help you find them quickly.
If you're trailering, it's a good idea to review these
sections before you start your trip.
Check periodically to see that all hitch nuts and bolts
are tight.
Trailer Wiring Harness
Heavy-Duty Trailer Wiring Package
Your vehicle is equipped with the seven-wire trailer
towing harness. This harness with a seven
-pin universal
heavy
-duty trailer connector is attached to a bracket on
the platform hitch.

5-
5-1
Section 5 Problems on the Road
Here you'll find what to do about some problems that can occur on the road.
5
-2 Hazard Warning Flashers
5
-2 Other Warning Devices
5
-3 Jump Starting
5
-9 Towing Your Vehicle
5
-9 Engine Overheating
5
-12 Cooling System5
-19 Engine Fan Noise
5
-19 If a Tire Goes Flat
5
-20 Changing a Flat Tire
5
-36 Spare Tire
5
-37 If You're Stuck: In Sand, Mud, Ice or Snow

5-4
2. Get the vehicles close enough so the jumper cables
can reach, but be sure the vehicles aren't touching
each other. If they are, it could cause a ground
connection you don't want. You wouldn't be able to
start your vehicle, and the bad grounding could
damage the electrical systems.
To avoid the possibility of the vehicles rolling, set
the parking brake firmly on both vehicles involved
in the jump start procedure. Put an automatic
transmission in PARK (P) or a manual transmission
in NEUTRAL before setting the parking brake.
NOTICE:
If you leave your radio on, it could be badly
damaged. The repairs wouldn't be covered by
your warranty.
3. Turn off the ignition on both vehicles. Unplug
unnecessary accessories plugged into the cigarette
lighter or accessory power outlets. Turn off the radio
and all lamps that aren't needed. This will avoid
sparks and help save both batteries. And it could
save your radio!
4. Open the hoods and locate the positive (+) and
negative (
-) terminal locations of the other vehicle.
Your vehicle has a remote positive (+) jump starting
terminal and a remote negative (
-) jump starting
terminal. You should always use these remote
terminals instead of the terminals on the battery.
The remote positive (+) terminal is located under a
red plastic cover near the engine accessory drive
bracket. To access the remote positive (+) terminal,
open the red plastic cover.
The remote negative (
-) terminal is located on
the engine accessory drive bracket and is
marked ªGNDº.
See ªEngine Compartment Overviewº in the Index
for more information on location.

5-5
CAUTION:
Using a match near a battery can cause battery
gas to explode. People have been hurt doing this,
and some have been blinded. Use a flashlight if
you need more light.
Be sure the battery has enough water. You don't
need to add water to the ACDelco
battery
installed in every new GM vehicle. But if a
battery has filler caps, be sure the right amount
of fluid is there. If it is low, add water to take
care of that first. If you don't, explosive gas could
be present.
Battery fluid contains acid that can burn you.
Don't get it on you. If you accidentally get it in
your eyes or on your skin, flush the place with
water and get medical help immediately.
5. Check that the jumper cables don't have loose or
missing insulation. If they do, you could get a shock.
The vehicles could be damaged too.
Before you connect the cables, here are some basic
things you should know. Positive (+) will go to
positive (+) or to a remote positive terminal (+) if the
vehicle has one. Negative (
-) will go to a heavy,
unpainted metal engine part or to a remote negative
(
-) terminal, if the vehicle has one.
Don't connect positive (+) to negative (
-) or you'll
get a short that would damage the battery and maybe
other parts too.
CAUTION:
Fans or other moving engine parts can injure you
badly. Keep your hands away from moving parts
once the engine is running.

5-6
6. Connect the red
positive (+) cable to
the positive (+) terminal
of the dead battery. Use
a remote positive (+)
terminal if the vehicle
has one.
7. Don't let the other end
touch metal. Connect it
to the positive (+)
terminal of the good
battery. Use a remote
positive (+) terminal if
the vehicle has one.
8. Now connect the black
negative (
-) cable to the
negative (
-) terminal of
the good battery. Use a
remote negative (
-)
terminal if the
vehicle has one.
Your vehicle's remote
negative (
-) terminal is
marked GND.
Don't let the other end touch anything until the next
step. The other end of the negative (
-) cable doesn't go
to the dead battery. It goes to a heavy, unpainted metal
engine part or to a remote negative (
-) terminal on the
vehicle with the dead battery.

5-7
9. Connect the other end
of the negative (
-)
cable at least 18 inches
(45 cm) away from the
dead battery, but not
near engine parts that
move.
The electrical connection is just as good there, and
the chance of sparks getting back to the battery is
much less.10. Now start the vehicle with the good battery and run
the engine for awhile.
11. Try to start the vehicle that had the dead battery.
If it won't start after a few tries, it probably
needs service.
NOTICE:
Damage to your vehicle may result from
electrical shorting if jumper cables are removed
incorrectly. To prevent electrical shorting, take
care that they don't touch each other or any
other metal. The repairs wouldn't be covered by
your warranty.