Engine GMC ENVOY 2002 Repair Manual

4-56 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.

4-58 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 a lower gear, under heavy
loads or hilly conditions.
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. When parking uphill, turn your
wheels away from the curb. When parking downhill,
turn your wheels into the curb.
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 then shift into PARK (P).
5. Release the regular brakes.

4-59
CAUTION:
It can be dangerous to get out of your vehicle if
the shift lever is not fully in PARK (P) with the
parking brake firmly set. Your vehicle can roll.
If you have left the engine running, the vehicle
can move suddenly. You or others could be
injured. To be sure your vehicle won't move, even
when you're on fairly level ground, use the steps
that follow.
Always put the shift lever fully in PARK (P) with
the parking brake firmly set.
If the transfer case on four-wheel drive vehicles is
in NEUTRAL, your vehicle will be free to roll,
even if your shift lever is in PARK (P). So, be
sure the transfer case is in a drive gear
-- not
in NEUTRAL. See ªFour
-Wheel Drive
(Automatic Transfer Case)º in the Index.
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.

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
-8 Towing Your Vehicle
5
-8 Engine Overheating5
-10 Cooling System
5
-17 Engine Fan Noise
5
-17 If a Tire Goes Flat
5
-18 Changing a Flat Tire
5
-31 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.
If you have a four
-wheel-drive vehicle, be sure the
transfer case is not in NEUTRAL (N).
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 (if equipped). Turn
off the radio and all lamps that aren't needed. This
will avoid sparks and help to save both batteries.
And it could save your radio!
4. Open both hoods and locate the batteries. Find the
positive (+) and negative (
-) terminals on each
battery. Your vehicle has a remote negative (
-) jump
starting terminal. You should always use this remote
terminal instead of the terminal on the battery. The
remote negative (
-) terminal is located on the front
engine lift bracket and is marked ªGND.º 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.
CAUTION:
Fans or other moving engine parts can injure you
badly. Keep your hands away from moving parts
once the engine is running.
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. And don't connect the negative (
-) cable to
the negative (
-) terminal on the dead battery because
this can cause sparks.

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.
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 the remote negative (
-) terminal on the
vehicle with the dead battery. The remote negative (
-)
terminal on your vehicle is located on the front engine
lift bracket and is marked ªGND.º

5-7
9. Connect the other end of
the negative (
-) cable to
the remote negative (
-)
terminal on the vehicle
with the dead battery.
10. Now start the vehicle with the good battery and run
the engine for a while.
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.
Jumper Cable Removal
A. Heavy, Unpainted Metal Engine Part or Remote
Negative (
-) Terminal
B. Good Battery or Remote Positive (+) and Remote
Negative (
-) Terminals
C. Dead Battery or Remote Positive (+) Terminal

5-8
To disconnect the jumper cables from both vehicles, do
the following:
1. Disconnect the black negative (
-) cable from the
vehicle that had the dead battery.
2. Disconnect the black negative (
-) cable from the
vehicle with the good battery.
3. Disconnect the red positive (+) cable from the
vehicle with the good battery.
4. Disconnect the red positive (+) cable from the
other vehicle.
Towing Your Vehicle
Consult your dealer or a professional towing service
if you need to have your disabled vehicle towed.
See ªRoadside Assistanceº in the Index.
If you want to tow your vehicle behind another vehicle
for recreational purposes (such as behind a motorhome),
see ªRecreational Vehicle Towingº in the Index.
Engine Overheating
You will find a coolant temperature gage on your
vehicle's instrument panel. See ªGagesº in the Index.
If Steam Is Coming From Your Engine

5-9
CAUTION:
Steam from an overheated engine can burn you
badly, even if you just open the hood. Stay away
from the engine if you see or hear steam coming
from it. Just turn it off and get everyone away
from the vehicle until it cools down. Wait until
there is no sign of steam or coolant before you
open the hood.
If you keep driving when your engine is
overheated, the liquids in it can catch fire. You or
others could be badly burned. Stop your engine if
it overheats, and get out of the vehicle until the
engine is cool.
NOTICE:
If your engine catches fire because you keep
driving with no coolant, your vehicle can be
badly damaged. The costly repairs would not be
covered by your warranty.
If No Steam Is Coming From Your Engine
If you get an engine overheat warning 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. See ªDriving on Gradesº in the Index.
If you get the overheat warning with no sign of steam,
try this for a minute or so:
1. If your air conditioner is on, turn it off.
2. Turn on your heater to full hot at the highest fan
speed and open the window as necessary.
3. If you're in a traffic jam, shift to NEUTRAL (N);
otherwise, shift to the highest gear while
driving
-- DRIVE (D) or THIRD (3).