light GMC SIERRA 1999 Repair Manual

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4-40
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 (or batteries) charged. You will need a
well
-charged battery (or batteries) to restart the vehicle,
and possibly for signaling later on with your headlamps.
Let the heater run for a while.
If you have a diesel engine, you may have to run it at a
higher speed to get enough heat. 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.

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Camper Wiring Harness
(If Equipped)
A five-wire harness may be stored under your vehicle.
The harness is located inside the frame rail and is even
with the front of the pickup box. 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 five
-wire camper harness and
the other connector to the wiring harness for the camper.
The technician can use the following color code chart
when connecting the wiring harness to your camper.
Brown: Rear Lamps

Yellow: Left Stoplamp and Turn Signal

Dark Green: Right Stoplamp and Turn Signal

White (Heavy Gage): Ground

Light Green: Back
-up Lamps
When the harness is not being used, store it in its
original place. Wrap the harness together and tie it
neatly so it won't be damaged.
Pickup Conversion to Chassis Cab
General Motors is aware that some vehicle owners may
consider having the pickup box removed and a
commercial or recreational body installed. Before you
do so, first contact the GM Customer Assistance Office
for your area for information on such conversions
specific to this vehicle. (See the ªWarranty and Owner
Assistanceº booklet for Customer Assistance Office.)
Owners should be aware that, as manufactured, there are
differences between a chassis cab and a pickup with the
box removed which may affect vehicle safety. The
components necessary to adapt a pickup to permit its
safe use with a specialized body should be installed by a
body builder in accordance with the information
available from the Customer Assistance Office.

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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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5-3
Other Warning Devices
If you carry reflective triangles, you can use them to
warn others. Set one up at the side of the road about
300 feet (100 m) behind your vehicle.
Jump Starting
If your battery (or batteries) have run down, you may
want to use another vehicle and some jumper cables
to start your vehicle. But please use the following steps
to do it safely.
CAUTION:
Batteries can hurt you. They can be
dangerous because:

They contain acid that can burn you.

They contain gas that can explode or ignite.

They contain enough electricity to
burn you.
If you don't follow these steps exactly, some or
all of these things can hurt you.
NOTICE:
Ignoring these steps could result in costly damage
to your vehicle that wouldn't be covered by
your warranty.
The ACDelco Freedom battery in your vehicle
has a built
-in hydrometer. Do not charge, test or
jump start the battery if the hydrometer looks
clear or light yellow. Replace the battery when
there is a clear or light yellow hydrometer and a
cranking complaint.
Trying to start your vehicle by pushing or pulling
it won't work, and it could damage your vehicle.
1. Check the other vehicle. It must have a 12-volt
battery with a negative ground system.
NOTICE:
If the other system isn't a 12-volt system with a
negative ground, both vehicles can 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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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 batteries have enough water.
You don't need to add water to the ACDelco
Freedom

battery (or batteries) 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.
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 (+) and negative (
-) will go to a heavy
unpainted metal engine part. Don't connect positive
(+) to negative (
-) or you'll get a short that would
damage the battery and maybe other parts too.
On vehicles equipped with dual batteries, make any
battery connections to the primary battery located on
the passenger's side of the vehicle.
CAUTION:
Fans or other moving engine parts can injure you
badly. Keep your hands away from moving parts
once the engine is running.

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5-33
NOTICE:
Spinning your wheels can destroy parts of your
vehicle as well as the tires. If you spin the wheels
too fast while shifting your transmission back
and forth, you can destroy your transmission.
For information about using tire chains on your vehicle,
see ªTire Chainsº in the Index.
Rocking Your Vehicle To Get It Out
First, turn your steering wheel left and right. That will
clear the area around your front wheels. If you have a
four
-wheel drive vehicle, shift into 4HI. Then shift back
and forth between REVERSE (R) and a forward gear
(or with a manual transmission, between FIRST (1) or
SECOND (2) and REVERSE (R)), spinning the wheels
as little as possible. Release the accelerator pedal while
you shift, and press lightly on the accelerator pedal
when the transmission is in gear. By slowly spinning
your wheels in the forward and reverse directions, you
will cause a rocking motion that may free your vehicle.
If that doesn't get you out after a few tries, you may
need to be towed out. Or, you can use your recovery
hooks if your vehicle has them. If you do need to be
towed out, see ªTowing Your Vehicleº in the Index.
Using the Recovery Hooks
Your vehicle may be equipped with recovery hooks.
The recovery hooks are provided at the front of your
vehicle. You may need to use them if you're stuck
off
-road and need to be pulled to some place where
you can continue driving.

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6-7
CAUTION:
If you get gasoline on yourself and then
something ignites it, you could be badly burned.
Gasoline can spray out on you if you open the
fuel filler cap too quickly. This spray can happen
if your tank is nearly full, and is more likely in
hot weather. Open the fuel filler cap slowly and
wait for any ªhissº noise to stop. Then unscrew
the cap all the way.
Be careful not to spill gasoline. Clean gasoline from
painted surfaces as soon as possible. See ªCleaning the
Outside of Your Vehicleº in the Index.When you put the cap back on, turn it to the right
(clockwise) until you hear a clicking sound. Make sure
you fully install the cap. The diagnostic system can
determine if the fuel cap has been left off or improperly
installed. This would allow fuel to evaporate into the
atmosphere. See ªMalfunction Indicator Lampº in
the Index.
NOTICE:
If you need a new cap, be sure to get the right
type. Your dealer can get one for you. If you get
the wrong type, it may not fit properly. This may
cause your malfunction indicator lamp to light
and your fuel tank and emissions system may be
damaged. See ªMalfunction Indicator Lampº in
the Index.

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6-24
Check the fluid level only when your engine is off, the
vehicle is parked on a level place and the transmission is
cool enough for you to rest your fingers on the
transmission case.
Then, follow these steps:
1. Remove the filler plug.
2. Check that the lubricant level is up to the bottom of
the filler plug hole.
3. If the fluid level is good, install the plug and be sure
it is fully seated. If the fluid level is low, add more
fluid as described in the next steps.
How to Add Fluid
Here's how to add fluid. Refer to the Maintenance
Schedule to determine what kind of fluid to use. See
ªRecommended Fluids and Lubricantsº in the Index.
1. Remove the filler plug.
2. Add fluid at the filler plug hole. Add only enough
fluid to bring the fluid level up to the bottom of the
filler plug hole.
3. Install the filler plug. Be sure the plug is fully seated.
Hydraulic Clutch
The hydraulic clutch system in your vehicle is
self
-adjusting. A slight amount of play (1/4 inch to
1/2 inch or 6 mm to 12 mm) in the pedal is normal.
It isn't a good idea to ªtop offº your clutch fluid.
Adding fluid won't correct a leak. A fluid loss in this
system could indicate a problem. Have the system
inspected and repaired.

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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.