1999 GMC SONOMA service

4-34
Highway Hypnosis
Is there actually such a condition as ªhighway hypnosisº?
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. Don't let it happen
to you! If it does, your vehicle can leave the road in less
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.
Hill and Mountain Roads
Driving on steep hills or mountains is different from
driving in flat or rolling terrain.
If you drive regularly in steep country, or if you're
planning to visit there, here are some tips that can make
your trips safer and more enjoyable. (See ªOff
-Road
Drivingº in the Index for information about
driving off
-road.)

4-39
CAUTION:
Snow can trap exhaust gases under your vehicle.
This can cause deadly CO (carbon monoxide) gas
to get inside. CO could overcome you and kill
you. You can't see it or smell it, so you might not
know it is in your vehicle. Clear away snow from
around the base of your vehicle, especially any
that is blocking your exhaust pipe. And check
around again from time to time to be sure snow
doesn't collect there.
Open a window just a little on the side of the
vehicle that's away from the wind. This will help
keep CO out.
Run your engine only as long as you must. This saves
fuel. When you run the engine, make it go a little faster
than just idle. That is, push the accelerator slightly. This
uses less fuel for the heat that you get and it keeps the
battery charged. You will need a well
-charged battery to
restart the vehicle, and possibly for signaling later on
with your headlamps. Let the heater run for a while.Then, shut the engine off and close the window almost
all the way to preserve the heat. Start the engine again
and repeat this only when you feel really uncomfortable
from the cold. But do it as little as possible. Preserve the
fuel as long as you can. To help keep warm, you can get
out of the vehicle and do some fairly vigorous exercises
every half hour or so until help comes.
Recreational Vehicle Towing
Your vehicle should not be towed with all four wheels
on the ground. Your transmission has no provision for
internal lubrication while being towed. To properly tow
your vehicle, it should be placed on a platform trailer
with all four wheels off the ground. Towing with all four
wheels on the ground should be avoided.
In rare cases when it's unavoidable and your vehicle must
be towed with all four wheels on the ground, the propeller
shaft to axle yoke orientation should be marked and the
propeller shaft removed following the applicable service
manual removal/installation procedure. See ªService and
Owner Publicationsº in the Index.

4-48
The following chart shows how much your trailer can
weigh, based upon your vehicle model and options.
VehicleAxle
Ratio Max. Trailer Wt.
2WD 2.2L
L4 Engine*#3.73
4.102,000 lbs. (908 kg)
2,300 lbs. (1 044 kg)
2WD ªVORTECº
4300 V6,
Auto. Trans.*3.08
3.425,400 lbs. (2 451 kg)
6,400 lbs. (2 905 kg)
2WD ªVORTECº
4300 V6,
Man. Trans.*3.08 4,200 lbs. (1 906 kg)
4WD ªVORTECº
4300 V6
Auto. Trans.3.08
3.42
3.734,900 lbs. (2 224 kg)
5,900 lbs. (2 678 kg)
5,900 lbs. (2 678 kg)
4WD ªVORTECº
4300 V6
Man. Trans.3.08
3.42
3.733,900 lbs. (1 770 kg)
4,400 lbs. (1 997 kg)
4,900 lbs. (2 224 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, see ªService Parts
Identification Labelº in the Index.# If your vehicle is equipped with a code 5 engine
you must use regular unleaded gasoline rated at
87 octane or higher when towing.
Optional body styles, equipment, passengers or cargo
will reduce trailer rating.
Maximum trailer weight is calculated assuming the
driver and one passenger are in the tow vehicle and it
has all the required trailering equipment. The weight of
additional optional equipment, passengers and cargo in
the tow vehicle must be subtracted from the maximum
trailer weight. The weight of the trailer tongue also
affects trailering capacity. See ªWeight of the Trailer
Tongueº later in this section.
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
1908 Colonel Sam Drive
Oshawa, Ontario L1H 8P7

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.

5-6
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 part on the engine of the vehicle with the
dead battery.
9. Attach the 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, but 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 with the dead battery. If it won't
start after a few tries, make sure all connections are
good. If it still won't start, it probably needs service.
CAUTION:
Fans or other moving engine parts can injure you
badly. Keep your hands away from moving parts
once the engine is running.
12. Remove the cables in reverse order to prevent
electrical shorting. Take care that they don't touch
each other or any other metal.
A. Heavy Unpainted Metal Engine Part
B. Good Battery
C. Dead Battery

5-7
Towing Your Vehicle
CAUTION:
To help avoid serious personal injury to you
or others:

Never let passengers ride in a vehicle that
is being towed.

Never tow faster than safe or posted speeds.

Never tow with damaged parts not
fully secured.

Never get under your vehicle after it has
been lifted by the tow truck.

Always secure the vehicle on each side with
separate safety chains when towing it.

Use only the correct hooks.
NOTICE:
Use the proper towing equipment to avoid
damage to the bumper, fascia or fog lamp areas
of the vehicle.
With current trends in automotive styles and design, it is
essential that the correct towing equipment is used to
tow a vehicle. Your vehicle can be towed with wheel lift
or car carrier equipment. Vehicles equipped with a
manual transmission must be placed on a towing dolly
when towed from the front. Two
-wheel-drive vehicles
must abide by the following tow limits when being
towed by wheel lift equipment:

Towing from the front
-- 35 mph (55 km/h),
50 miles (80 km)

Towing from the rear
-- 35 mph (55 km/h),
50 miles (80 km)
When towing four
-wheel-drive vehicles with the
electronic shift transfer case with wheel lift equipment, a
towing dolly must be used under the rear wheels when
towing from the front and the front wheels when towing
from the rear.
Consult your dealer or a professional towing service if
you need to have your vehicle towed. See ªRoadside
Assistanceº in the Index.

5-9 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 you have an air conditioner and it's 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) for
automatic transmissions.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, 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 vehicle until it
cools down.
You may decide not to lift the hood but to get service
help right away.

5-11
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 engine fire, and you could be burned.
Get any leak fixed before you drive the vehicle.
NOTICE:
Engine damage from running your engine
without coolant isn't covered by your warranty.
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 occurs first. Damage caused by the
use of coolant other than DEX
-COOL
is not
covered by your new vehicle warranty.
If there seems to be no leak, start the engine again.
See if the engine cooling fan speed increases when idle
speed is doubled by pushing the accelerator pedal
down. If it doesn't, your vehicle needs service.
Turn off the engine.