2004 GMC SONOMA service

Off-Road Driving with Your
Four-Wheel-Drive Vehicle
This off-road guide is for vehicles that have four-wheel
drive.
Also, seeAnti-Lock BrakesunderBraking on page 4-6.
Off-road driving can be great fun. But it does have
some definite hazards. The greatest of these is
the terrain itself.
“Off-roading” means you have left the great North
American road system behind. Traffic lanes are not
marked. Curves are not banked. There are no
road signs. Surfaces can be slippery, rough, uphill or
downhill. In short, you have gone right back to nature.
Off-road driving involves some new skills. And that
is why it is very important that you read this guide.
You will find many driving tips and suggestions.
These will help make your off-road driving safer and
more enjoyable.
Before You Go Off-Roading
There are some things to do before you go out. For
example, be sure to have all necessary maintenance
and service work done. Check to make sure all
underbody shields (if so equipped) are properly
attached. Be sure you read all the information about
your four-wheel-drive vehicle in this manual. Is there
enough fuel? Is the spare tire fully inflated? Are the fluid
levels up where they should be? What are the local
laws that apply to off-roading where you will be driving?
If you do not know, you should check with law
enforcement people in the area. Will you be on
someone’s private land? If so, be sure to get the
necessary permission.
Loading Your Vehicle for Off-Road
Driving
There are some important things to remember about
how to load your vehicle.
•The heaviest things should be on the load floor and
forward of your rear axle. Put heavier items as far
forward as you can.
•Be sure the load is secured properly, so driving on
the off-road terrain does not toss things around.
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After Off-Road Driving
Remove any brush or debris that has collected on the
underbody, 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,
steering, suspension, wheels, tires and exhaust
system for damage. Also, check the fuel lines and
cooling system for any leakage.
Your vehicle will require more frequent service due to
off-road use. Refer to the Maintenance Schedule
for additional information.
Driving at Night
Night driving is more dangerous than day driving.
One reason is that some drivers are likely to be
impaired — by alcohol or drugs, with night vision
problems, or by fatigue.
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Just before you leave the lane, glance quickly over your
shoulder to make sure there is not another vehicle in
your “blind” spot.
Once you are moving on the freeway, make certain you
allow a reasonable following distance. Expect to
move slightly slower at night.
When you want to leave the freeway, move to the
proper lane well in advance. If you miss your exit, do
not, under any circumstances, stop and back up. Drive
on to the next exit.
The exit ramp can be curved, sometimes quite sharply.
The exit speed is usually posted.
Reduce your speed according to your speedometer, not
to your sense of motion. After driving for any distance
at higher speeds, you may tend to think you are
going slower than you actually are.Before Leaving on a Long Trip
Make sure you are ready. Try to be well rested. If you
must start when you are not fresh — such as after
a day’s work — do not plan to make too many miles that
first part of the journey. Wear comfortable clothing
and shoes you can easily drive in.
Is your vehicle ready for a long trip? If you keep it
serviced and maintained, it is ready to go. If it needs
service, have it done before starting out. Of course, you
will find experienced and able service experts in GM
dealerships all across North America. They will be ready
and willing to help if you need it.
Here are some things you can check before a trip:
•Windshield Washer Fluid:Is the reservoir full? Are
all windows clean inside and outside?
•Wiper Blades:Are they in good shape?
•Fuel, Engine Oil, Other Fluids:Have you checked
all levels?
•Lamps:Are they all working? Are the lenses clean?
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•Tires:They are vitally important to a safe,
trouble-free trip. Is the tread good enough for
long-distance driving? Are the tires all inflated to the
recommended pressure?
•Weather Forecasts:What is the weather outlook
along your route? Should you delay your trip a
short time to avoid a major storm system?
•Maps:Do you have up-to-date maps?
Highway Hypnosis
Is there actually such a condition as “highway
hypnosis”? Or is it just plain falling asleep at the wheel?
Call it highway hypnosis, lack of awareness, or
whatever.
There is something about an easy stretch of road with
the same scenery, along with the hum of the tires on the
road, the drone of the engine, and the rush of the
wind against the vehicle that can make you sleepy. Do
not let it happen to you! If it does, your vehicle can
leave the road inless than a second,and you could
crash and be injured.What can you do about highway hypnosis? First, be
aware that it can happen.
Then here are some tips:
•Make sure your vehicle is well ventilated, with a
comfortably cool interior.
•Keep your eyes moving. Scan the road ahead and
to the sides. Check your mirrors and your
instruments frequently.
•If you get sleepy, pull off the road into a rest,
service or parking area and take a nap, get some
exercise, or both. For safety, treat drowsiness
on the highway as an emergency.
4-35

Towing
Towing Your Vehicle
Consult your dealer or a professional towing service if
you need to have your disabled vehicle towed. See
Roadside Assistance Program on page 7-6.
If you want to tow your vehicle behind another vehicle
for recreational purposes (such as behind a motorhome),
see “Recreational Vehicle Towing” following.
Recreational Vehicle Towing
Recreational vehicle towing means towing your vehicle
behind another vehicle — such as behind a motorhome.
The two most common types of recreational vehicle
towing are known as “dinghy towing” (towing your
vehicle with all four wheels on the ground) and “dolly
towing” (towing your vehicle with two wheels on
the ground and two wheels up on a device known
as a “dolly”).
Your vehicle was not designed to be towed with any of
its wheels on the ground. If your vehicle must be
towed, seeTowing Your Vehicle on page 4-45.
Loading Your Vehicle
It is very important to know how much weight your
vehicle can carry. This weight is called the vehicle
capacity weight and includes the weight of all occupants,
cargo and all nonfactory-installed options. Two labels
on your vehicle show how much weight it may properly
carry, the Tire and Loading Information label and the
Certification/Tire label.
{CAUTION:
Do not load your vehicle any heavier than the
GVWR, or either the maximum front or rear
GAWR. If you do, parts on your vehicle can
break, and it can change the way your vehicle
handles. These could cause you to lose
control and crash. Also, overloading can
shorten the life of your vehicle.
4-45

Vehicle* Axle RatioMaximum Trailer
WeightGCWR**
4WD Crew Cab®
4.3L V6/Auto. Trans.3.42
3.735,200 lbs. (2 361 kg)
5,200 lbs. (2 361 kg)9,500 lbs. (4 309 kg)
9,500 lbs. (4 309 kg)
* If your vehicle is equipped with RPO V4A (Xtreme™
Sport Appearance Package), your vehicle was
neither intended nor designed to tow a trailer. For more
information on RPO codes, seeService Parts
Identication Label on page 5-94.
**The Gross Combination Weight Rating (GCWR) is the
total allowable weight of the completely loaded vehicle
and trailer including any passengers, cargo, equipment
and conversions. The GCWR for your vehicle should
not be exceeded.
You can ask your dealer for our trailering information or
advice, or you can write us at the address listed in
your Warranty and Owner Assistance Information
Booklet.
In Canada, write to:
General Motors of Canada Limited
Customer Communication Centre, 163-005
1908 Colonel Sam Drive
Oshawa, Ontario L1H 8P7
Weight of the Trailer Tongue
The tongue load (A) of any trailer is an important weight
to measure because it affects the total or gross weight
of your vehicle. The Gross Vehicle Weight (GVW)
includes the curb weight of the vehicle, any cargo you
may carry in it, and the people who will be riding in
the vehicle. If you have a lot of options, equipment,
passengers or cargo in your vehicle, it will reduce the
tongue weight your vehicle can carry, which will
also reduce the trailer weight your vehicle can tow. And
if you will tow a trailer, you must add the tongue load
to the GVW because your vehicle will be carrying
that weight, too. SeeLoading Your Vehicle on page 4-45
for more information about your vehicle’s maximum
load capacity.
4-57

4. Reapply the regular brakes. Then apply your
parking brake, and then shift into PARK (P), or
REVERSE (R) for a manual transmission.
5. If you have a four-wheel-drive vehicle with an
automatic transfer case, be sure the transfer case is
in a drive gear–not in NEUTRAL.
6. Release the regular brakes.
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. SeePart A: Scheduled Maintenance
Services on page 6-4for 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.
4-63

Service............................................................5-3
Doing Your Own Service Work.........................5-3
Adding Equipment to the Outside of
Your Vehicle..............................................5-4
Fuel................................................................5-4
Gasoline Octane............................................5-4
Gasoline Specifications....................................5-5
California Fuel...............................................5-5
Additives.......................................................5-6
Fuels in Foreign Countries...............................5-6
Filling Your Tank............................................5-7
Filling a Portable Fuel Container.......................5-9
Checking Things Under
the Hood....................................................5-10
Hood Release..............................................5-10
Engine Compartment Overview.......................5-12
Engine Oil...................................................5-13
Engine Air Cleaner/Filter................................5-18
Automatic Transmission Fluid.........................5-19
Engine Coolant.............................................5-23
Radiator Pressure Cap..................................5-26
Engine Overheating.......................................5-26
Cooling System............................................5-28
Engine Fan Noise.........................................5-35
Power Steering Fluid.....................................5-35Windshield Washer Fluid................................5-36
Brakes........................................................5-37
Battery........................................................5-40
Jump Starting...............................................5-41
Rear Axle.......................................................5-46
Four-Wheel Drive............................................5-46
Front Axle......................................................5-47
Bulb Replacement..........................................5-48
Halogen Bulbs..............................................5-48
Headlamps..................................................5-49
One-Piece Front Turn Signal Lamps................5-51
Two-Piece Front Turn Signal Lamps................5-51
Center High-Mounted Stoplamp (CHMSL).........5-52
Taillamps.....................................................5-53
Replacement Bulbs.......................................5-54
Windshield Wiper Blade Replacement..............5-54
Tires..............................................................5-57
Inflation - Tire Pressure.................................5-67
Tire Inspection and Rotation...........................5-68
When It Is Time for New Tires.......................5-69
Buying New Tires.........................................5-70
Uniform Tire Quality Grading..........................5-71
Wheel Alignment and Tire Balance..................5-72
Wheel Replacement......................................5-72
Section 5 Service and Appearance Care
5-1