brake light GMC SIERRA 1999 User Guide

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4-7
If your engine ever stops while you're driving, brake
normally but don't pump your brakes. If you do, the
pedal may get harder to push down. If your engine
stops, you will still have some power brake assist. But
you will use it when you brake. Once the power assist is
used up, it may take longer to stop and the brake pedal
will be harder to push.
Anti-Lock Brakes (ABS)
Your vehicle has anti-lock brakes (ABS). ABS is an
advanced electronic braking system that will help
prevent a braking skid.
When you start your engine and begin to drive away,
your anti
-lock brake system will check itself. You may
hear a momentary motor or clicking noise while this test
is going on. This is normal.
If there's a problem with the
anti
-lock brake system, this
warning light will stay on.
See ªAnti
-Lock Brake
System Warning Lightº in
the Index.
Here's how anti-lock works. Let's say the road is wet.
You're driving safely. Suddenly an animal jumps out in
front of you.
You slam on the brakes. Here's what happens with ABS.
A computer senses that wheels are slowing down. If one
of the wheels is about to stop rolling, the computer will
separately work the brakes at each front wheel and at
both rear wheels.

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4-22 Driving Downhill
When off-roading takes you downhill, you'll want to
consider a number of things:

How steep is the downhill? Will I be able to maintain
vehicle control?

What's the surface like? Smooth? Rough? Slippery?
Hard
-packed dirt? Gravel?

Are there hidden surface obstacles? Ruts?
Logs? Boulders?

What's at the bottom of the hill? Is there a hidden
creek bank or even a river bottom with large rocks?
If you decide you can go down a hill safely, then try to
keep your vehicle headed straight down, and use a low
gear. This way, engine drag can help your brakes and
they won't have to do all the work. Descend slowly,
keeping your vehicle under control at all times.
CAUTION:
Heavy braking when going down a hill can cause
your brakes to overheat and fade. This could
cause loss of control and a serious accident. Apply
the brakes lightly when descending a hill and use
a low gear to keep vehicle speed under control.
Q:Are there some things I should not do when
driving down a hill?
A:Yes! These are important because if you
ignore them you could lose control and have
a serious accident.

When driving downhill, avoid turns that take you
across the incline of the hill. A hill that's not too
steep to drive down may be too steep to drive across.
You could roll over if you don't drive straight down.

Never go downhill with the transmission in
NEUTRAL (N), or with the clutch pedal depressed
in a manual shift. This is called ªfree
-wheeling.º
Your brakes will have to do all the work and could
overheat and fade.

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4-26 Driving in Water
Light rain causes no special off-road driving problems.
But heavy rain can mean flash flooding, and flood
waters demand extreme caution.
Find out how deep the water is before you drive through
it. If it's deep enough to cover your wheel hubs, axles or
exhaust pipe, don't try it
-- you probably won't get
through. Also, water that deep can damage your axle
and other vehicle parts.
If the water isn't too deep, then drive through it slowly.
At fast speeds, water splashes on your ignition system
and your vehicle can stall. Stalling can also occur if you
get your tailpipe under water. And, as long as your
tailpipe is under water, you'll never be able to start your
engine. When you go through water, remember that when
your brakes get wet, it may take you longer to stop.
CAUTION:
Driving through rushing water can be dangerous.
Deep water can sweep your vehicle downstream
and you and your passengers could drown. If it's
only shallow water, it can still wash away the
ground from under your tires, and you could lose
traction and roll the vehicle over. Don't drive
through rushing water.
See ªDriving Through Waterº in the Index for more
information on driving through water.
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.

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4-30
CAUTION:
Wet brakes can cause accidents. They won't work
as well in a quick stop and may cause pulling to
one side. You could lose control of the vehicle.
After driving through a large puddle of water or
a car wash, apply your brake pedal lightly until
your brakes work normally.
Hydroplaning
Hydroplaning is dangerous. So much water can build up
under your tires that they can actually ride on the water.
This can happen if the road is wet enough and you're
going fast enough. When your vehicle is hydroplaning,
it has little or no contact with the road.
Hydroplaning doesn't happen often. But it can if your
tires do not have much tread or if the pressure in one or
more is low. It can happen if a lot of water is standing on
the road. If you can see reflections from trees, telephone
poles or other vehicles, and raindrops ªdimpleº the
water's surface, there could be hydroplaning.Hydroplaning usually happens at higher speeds. There
just isn't a hard and fast rule about hydroplaning. The
best advice is to slow down when it is raining.
Driving Through Deep Standing Water
NOTICE:
If you drive too quickly through deep puddles or
standing water, water can come in through your
engine's air intake and badly damage your
engine. Never drive through water that is slightly
lower than the underbody of your vehicle. If you
can't avoid deep puddles or standing water, drive
through them very slowly.
Some Other Rainy Weather Tips

Besides slowing down, allow some extra following
distance. And be especially careful when you pass
another vehicle. Allow yourself more clear room
ahead, and be prepared to have your view restricted
by road spray.

Have good tires with proper tread depth.
(See ªTiresº in the Index.)

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4-60 Trailer Wiring Harness
A. Light-Duty Wiring Harness
B. Additional Heavy
-Duty Wiring
C. Tie Straps
An eight
-wire harness is stored under the rear end of
your vehicle. Five wires (A) are located between the rear
bumper and the spare tire, near the center. This wiring
harness is tie
-strapped to the taillamp and stoplamp
harness. Three wires (B) (light gauge white, blue and
orange) are located at the rear left hand frame rail.This harness has a 30
-amp battery feed wire and no
connector, and should be wired by a qualified electrical
technician. After choosing an aftermarket mating
connector pair, have the technician attach one connector
to the eight
-wire trailer harness and the other connector
to the wiring harness on the trailer. Be sure that the
wiring harness on the trailer is strapped to the trailer's
frame and leave it loose enough so that the wiring
doesn't bend or break, but not so loose that it drags on
the ground. The technician can use the following color
code chart when connecting the wiring harness to
your trailer.

Brown: Rear Lamps

Yellow: Left Stoplamp and Turn Signal

Dark Green: Right Stoplamp and Turn Signal

White (Heavy Gauge): Ground

Light Green: Back
-up Lamps

White (Light Gauge): Center High
-Mounted
Stop Lamp

Blue: Auxiliary/Electric Trailer Brake Circuit

Orange: Fused Auxiliary Circuit
Store the harness in its original place. Wrap the harness
together and tie it neatly so it won't be damaged.

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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 (N). If you have a four
-wheel-drive
vehicle, be sure the transfer case is not in
NEUTRAL (N).
3. Turn off the ignition on both vehicles. Unplug
unnecessary accessories plugged into the cigarette
lighter or accessory power outlets. Turn off all lamps
that aren't needed as well as radios. This will avoid
sparks and help save both batteries. In addition, it
could save your radio!
NOTICE:
If you leave your radio on, it could be badly
damaged. The repairs wouldn't be covered by
your warranty.
4. Open the hoods and locate the batteries. Find the
positive (+) and negative (
-) terminals on each battery.
CAUTION:
If your vehicle has air conditioning, the auxiliary
electric fan under the hood can start up even
when the engine is not running and can injure
you. Keep hands, clothing and tools away from
any underhood electric fan.

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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 torque wheel nuts in the
proper sequence to GM 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.ºBrake 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 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.

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6-73
Fuse/Circuit
Breaker Usage
20 PRNDL, Automatic Transmission,
Speedometer, Check Gages
Warning Light
21 Security/Steering
22 Not Used
23 Not Used
24 Front Axle, 4WD Indicator Lamp,
TP2 Relay (Gasoline Engine)
A Power Door Lock, Six
-Way Power
Seat, Keyless Entry Module
B Power WindowsUnderhood Fuse/Relay Center
The underhood fuse/relay center is located in the rear of
the engine compartment near the brake fluid reservoir.
Move the retainer clips for the cover to access the
fuse block.
You can remove fuses with a fuse extractor. The fuse
extractor is mounted to the interior fuse block. To
remove fuses if you don't have a fuse extractor, hold the
end of the fuse between your thumb and index finger
and pull straight out.

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6-74
Name Usage
ECM
-B Fuel Pump, PCM/VCM
RR DEFOG Rear Window Defogger
IGN
-E Auxiliary Fan Relay Coil,
A/C Compressor Relay,
Hot Fuel Module, Dual Tanks
HORN Horn, Underhood Lamps
AUX FAN Auxiliary FanName Usage
ECM
-1 Injectors, PCM/VCM, Fuel
Solenoid (Diesel Engine, Fuel
Control Module (Diesel Engine)
HTD ST
-FR Not Used
A/C Air Conditioning
HTD MIR Not Used
ENG
-1 Ignition Switch, EGR, Canister
Purge, EVRV Idle Coast Solenoid,
MAF, Heated O
2,
Fuel Heater (Diesel Engine),
Water Sensor (Diesel Engine),
Boost Solenoid (Diesel Engine),
EPR (Diesel Engine)
HTD ST
-RR Not Used
LIGHTING Headlamp and Panel Dimmer
Switch, Fog and Courtesy Fuses
BATT Battery, Fuse Block Busbar
IGN
-A Ignition Switch
IGN
-B Ignition Switch
ABS Anti
-Lock Brake Module
BLOWER High Blower Relay
STOP/HAZ Stoplamps
HEATED SEATS Not Used

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9-1
Section 9 Index
A
ccessory Power Outlet 2-59 . . . . . . . . . . . . . . . . . . . . . . . . .
Adding Equipment to the Outside of Your Vehicle 6-3 . . . . . .
Air Bag 1-23 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Adding Equipment 1-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
How Does it Restrain 1-28 . . . . . . . . . . . . . . . . . . . . . . . . . .
How it Works 1-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Location 1-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Off Light 2-65 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Off Switch 1-30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Readiness Light 1-25, 2-65 . . . . . . . . . . . . . . . . . . . . . . . . .
Servicing 1-33 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
What Makes it Inflate 1-27 . . . . . . . . . . . . . . . . . . . . . . . . . .
What Will You See After it Inflates 1-28 . . . . . . . . . . . . . . .
When Should it Inflate 1-27 . . . . . . . . . . . . . . . . . . . . . . . . .
Air Cleaner 6-17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Cleaner Filter Restriction Indicator Check 7-42 . . . . . . . .
Air Conditioning 3-3, 3-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Air Conditioning Refrigerants 6-78 . . . . . . . . . . . . . . . . . . . . .
Alignment and Balance, Tire 6-58 . . . . . . . . . . . . . . . . . . . . . .
Aluminum Wheels, Cleaning 6-66 . . . . . . . . . . . . . . . . . . . . . .
Antenna 3-27 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Antifreeze 6-28, 6-76, 7-48 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Anti-Lock
Brake System Warning Light 2-68, 4-7 . . . . . . . . . . . . . . . .
Brakes 4-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appearance Care 6
-61 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Appearance Materials, GM Vehicle Care/ 6-68 . . . . . . . . . . . .
Arbitration Program 8-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Armrest Storage Compartment 2-56 . . . . . . . . . . . . . . . . . . . .
Ashtrays 2-57 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Audio Equipment, Adding 3-25 . . . . . . . . . . . . . . . . . . . . . . . .
Audio Systems 3-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Automatic Transmission
Check 7
-42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fluid 6-20, 7-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Park Mechanism Check 7-45 . . . . . . . . . . . . . . . . . . . . . . . .
Starting Your Engine 2-13 . . . . . . . . . . . . . . . . . . . . . . . . . .
Operation 2-16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Axle, Front 6-27, 7-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Axle, Locking Rear 2-32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Axle, Rear 6-25, 7-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Battery 6-38 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jump Starting 5-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Replacement, Keyless Entry 2-8 . . . . . . . . . . . . . . . . . . . . .
Warnings 5-3, 5-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
BBB Auto Line 8-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Better Business Bureau Mediation 8-4 . . . . . . . . . . . . . . . . . . .
Blizzard, Driving In 4-38 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .