2002 GMC SONOMA four wheel drive

6-36
NOTICE:

Using the wrong fluid can badly damage
brake system parts. For example, just a few
drops of mineral
-based oil, such as engine
oil, in your brake system can damage brake
system parts so badly that they'll have to be
replaced. Don't let someone put in the
wrong kind of fluid.

If you spill brake fluid on your vehicle's
painted surfaces, the paint finish can be
damaged. Be careful not to spill brake fluid
on your vehicle. If you do, wash it off
immediately. See ªAppearance Careº in
the Index.
Brake Wear
If you have four-wheel drive, your vehicle has
four
-wheel disc brakes. If not, your vehicle has front
disc brakes and rear drum brakes.
Disc brake pads have built
-in wear indicators that make
a high
-pitched warning sound when the brake pads are
worn and new pads are needed. The sound may come
and go or be heard all the time your vehicle is moving
(except when you are pushing on the brake pedal
firmly).
CAUTION:
The brake wear warning sound means that soon
your brakes won't work well. That could lead to
an accident. When you hear the brake wear
warning sound, have your vehicle serviced.

6-37
NOTICE:
Continuing to drive with worn-out brake pads
could result in costly brake repair.
Some driving conditions or climates may cause a
brake squeal when the brakes are first applied or lightly
applied. This does not mean something is wrong with
your brakes.
Properly torqued wheel nuts are necessary to help
prevent brake pulsation. When tires are rotated, inspect
brake pads for wear and evenly tighten wheel nuts in the
proper sequence to GM torque specifications.
If you have rear drum brakes, they don't have wear
indicators, but if you ever hear a rear brake rubbing
noise, have the rear brake linings inspected immediately.
Also, the rear brake drums should be removed and
inspected each time the tires are removed for rotation or
changing. When you have the front brake pads replaced,
have the rear brakes inspected, too.
Brake linings should always be replaced as complete
axle sets.
See ªBrake System Inspectionº in Section 7 of this
manual under Part C ªPeriodic Maintenance
Inspections.º
Brake Pedal Travel
See your dealer if the brake pedal does not return to
normal height, or if there is a rapid increase in pedal
travel. This could be a sign of brake trouble.
Brake Adjustment
Every time you make a brake stop, your disc brakes
adjust for wear.
If you don't have four
-wheel drive and your brake pedal
goes down farther than normal, your rear drum brakes
may need adjustment. Adjust them by backing up and
firmly applying the brakes a few times.
Replacing Brake System Parts
The braking system on a vehicle is complex. Its
many parts have to be of top quality and work well
together if the vehicle is to have really good braking.
Your vehicle was designed and tested with top
-quality
GM brake parts.

6-55 Tire Chains
CAUTION:
If your vehicle has P235/75R15, P235/70R15,
P235/55R16 or 31x10.50R15LT/C size tires, don't
use tire chains. They can damage your vehicle
because there's not enough clearance.
Tire chains used on a vehicle without the proper
amount of clearance can cause damage to the
brakes, suspension or other vehicle parts. The
area damaged by the tire chains could cause you
to lose control of your vehicle and you or others
may be injured in a crash.
Use another type of traction device only if its
manufacturer recommends it for use on your vehicle
and tire size combination and road conditions.
Follow that manufacturer's instructions. To help
avoid damage to your vehicle, drive slowly, readjust
or remove the device if it's contacting your vehicle,
and don't spin your wheels.
If you do find traction devices that will fit, install
them on the rear tires.
NOTICE:
If your vehicle has a tire size other than
P235/75R15, P235/70R15, P235/55R16 or
31x10.50R15LT/C, use tire chains only where
legal and only when you must. Use only SAE
Class ªSº type chains that are the proper size for
your tires. Install them on the drive axle tires
(four
-wheel-drive vehicles can use chains on both
axles) and tighten them as tightly as possible with
the ends securely fastened. Drive slowly and
follow the chain manufacturer's instructions.
If you can hear the chains contacting your
vehicle, stop and retighten them. If the contact
continues, slow down until it stops. Driving too
fast or spinning the wheels with chains on will
damage your vehicle.

6-71
Name Usage
B/U LP Back
-Up Lamps
A/C Air Conditioning
W/W PMP Not Used
HORN Horn
IGN B Column Feed, IGN 2, 3, 4
RAP Retained Accessory Power
LD LEV Not Used
OXYSEN Oxygen Sensor
IGN E Engine
MIR/LKS Mirrors, Door Locks
FOG LP Fog Lamps
IGN A Starting and Charging IGN 1
STUD #2 Accessory Feeds, Electric Brake
PARKLP Parking Lamps
LR PRK Left Rear Parking LampsName Usage
IGN C Starter Solenoid,
Fuel Pump, PRNDL
HTDSEAT Heated Seat
HVAC HVAC System
TRCHMSL Not Used
RRDFOG Not Used
TBC Truck Body Computer
CRANK Clutch Switch, NSBU Switch
HAZLP Hazard Lamps
VECHMSL Vehicle Center High
-Mounted
Stoplamp
HTDMIR Heated Outside Mirrors
ATC Transfer Case (Four
-Wheel Drive)
STOPLP Stoplamps
RR W/W Not Used

7-4
Part A: Scheduled Maintenance
Services
Using Your Maintenance Schedule
We at General Motors want to help you keep your
vehicle in good working condition. But we don't know
exactly how you'll drive it. You may drive very short
distances only a few times a week. Or you may drive
long distances all the time in very hot, dusty weather.
You may use your vehicle in making deliveries.
Or you may drive it to work, to do errands or in many
other ways.
Because of all the different ways people use their
vehicles, maintenance needs vary. You may need more
frequent checks and replacements. So please read the
following and note how you drive. If you have any
questions on how to keep your vehicle in good
condition, see your dealer.
This part tells you the maintenance services you should
have done and when you should schedule them. If you
go to your dealer for your service needs, you'll know
that GM
-trained and supported service people will
perform the work using genuine GM parts.The proper fluids and lubricants to use are listed in
Part D. Make sure whoever services your vehicle
uses these. All parts should be replaced and all
necessary repairs done before you or anyone else
drives the vehicle.
These schedules are for vehicles that:

carry passengers and cargo within recommended
limits. You will find these limits on your vehicle's
Certification/Tire label. See ªLoading Your Vehicleº
in the Index.

are driven on reasonable road surfaces within legal
driving limits.

are driven off
-road in the recommended manner. See
ªOff
-Road Driving With Your Four-Wheel-Drive
Vehicleº in the Index.

use the recommended fuel. See ªFuelº in the Index.
Selecting the Right Schedule
First you'll need to decide which of the two schedules is
right for your vehicle. Here's how to decide which
schedule to follow:

7-52 Fuel System Inspection
Inspect the complete fuel system for damage or leaks.
Engine Cooling System Inspection
Inspect the hoses and have them replaced if they are
cracked, swollen or deteriorated. Inspect all pipes,
fittings and clamps; replace as needed. Clean the outside
of the radiator and air conditioning condenser. To help
ensure proper operation, a pressure test of the cooling
system and pressure cap is recommended at least
once a year.
Throttle System Inspection
Inspect the throttle system for interference or binding,
and for damaged or missing parts. Replace parts as
needed. Replace any components that have high effort
or excessive wear. Do not lubricate accelerator and
cruise control cables.
Transfer Case and Front Axle
(Four-Wheel Drive) Inspection
Every 12 months or at engine oil change intervals, check
front axle and transfer case and add lubricant when
necessary. A fluid loss could indicate a problem; check
and have it repaired, if needed. Check vent hose at
transfer case for kinks and proper installation. More
frequent lubrication may be required on off
-road use.
Brake System Inspection
Inspect the complete system. Inspect brake lines and
hoses for proper hook
-up, binding, leaks, cracks,
chafing, etc. Inspect disc brake pads for wear and rotors
for surface condition. Also inspect drum brake linings
for wear and cracks. Inspect other brake parts, including
drums, wheel cylinders, calipers, parking brake, etc.
Check parking brake adjustment. You may need to have
your brakes inspected more often if your driving habits
or conditions result in frequent braking.