1999 GMC SIERRA light

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6-70 Headlamps
The headlamp wiring is protected by an internal circuit
breaker. An electrical overload will cause the lamps
to go on and off, or in some cases to remain off.
If this happens, have your headlamp wiring checked
right away.
Windshield Wipers
The windshield wiper motor is protected by a circuit
breaker and a fuse. If the motor overheats due to heavy
snow, etc., the wiper will stop until the motor cools. If
the overload is caused by some electrical problem and
not snow, etc., be sure to get it fixed.
Power Windows and Other Power Options
Circuit breakers protect the power windows and other
power accessories. When the current load is too heavy,
the circuit breaker opens and closes, protecting the
circuit until the problem is fixed or goes away.
Fuses and Circuit Breakers
The wiring circuits in your vehicle are protected from
short circuits by a combination of fuses, circuit breakers
and fusible thermal links. This greatly reduces the
chance of fires caused by electrical problems.
Look at the silver
-colored band inside the fuse. If the
band is broken or melted, replace the fuse. Be sure you
replace a bad fuse with a new one of the identical size
and rating.
If you ever have a problem on the road and don't have
a spare fuse, you can borrow one that has the same
amperage. Just pick some feature of your vehicle that
you can get along without
-- like the radio or cigarette
lighter
-- and use its fuse, if it is the correct amperage.
Replace it as soon as you can.

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6-72
Fuse/Circuit
Breaker Usage
3 Courtesy Lamps, Cargo Lamp,
Glove Box Lamp, Dome/Reading
Lamps, Vanity Mirrors,
Power Mirrors
4 Instrument Cluster, DRL Relay,
Lamp Switch, Keyless Entry,
Low Coolant Module, Illuminated
Entry Module,
DRAC (Diesel Engine)
5 Not Used
6 Cruise Control
7 Auxiliary Power Outlet
8 Crank
9 License Lamp, Parking Lamps,
Taillamps, Roof Marker Lamps,
Tailgate Lamps, Front
Sidemarkers, Fog Lamp Relay,
Door Switch Illumination,
Fender Lamps, Headlamp
Switch IlluminationFuse/Circuit
Breaker Usage
10 Not Used
11 Wiper Motor, Washer Pump
12 A/C, A/C Blower,
High Blower Relay
13 Power Amp, Cigarette Lighter,
Door Lock Relay,
Power Lumbar Seat
14 4WD Indicator, Cluster, Comfort
Controls, Instrument Switches,
Radio Illumination,
Chime Module
15 DRL Relay, Fog Lamp Relay
16 Front and Rear Turn Signals,
Back
-Up Lamps, BTSI Solenoid
17 Radio (Ignition)
18 4WAL/VCM, ABS,
Cruise Control
19 Radio (Battery)

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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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7-42 At Least Twice a Year
Restraint System Check
Make sure the safety belt reminder light and all your
belts, buckles, latch plates, retractors and anchorages are
working properly. Look for any other loose or damaged
safety belt system parts. If you see anything that might
keep a safety belt system from doing its job, have it
repaired. Have any torn or frayed safety belts replaced.
Also look for any opened or broken air bag coverings,
and have them repaired or replaced. (The air bag system
does not need regular maintenance.)
Wiper Blade Check
Inspect wiper blades for wear or cracking. Replace blade
inserts that appear worn or damaged or that streak or
miss areas of the windshield. Also see ªWiper Blades,
Cleaningº in the Index.
Air Cleaner Filter Restriction Indicator Check
Your vehicle has an indicator located on the air cleaner in
the engine compartment that lets you know when the air
cleaner filter is dirty and needs to be changed. Check
indicator at least twice a year or when your oil is changed,
whichever occurs first. See ªAir Cleanerº in the Index for more information.
Inspect your air cleaner filter restriction indicator more
often if the vehicle is used in dusty areas or under off
road conditions.
Weatherstrip Lubrication
Silicone grease on weatherstrips will make them last
longer, seal better, and not stick or squeak. Apply
silicone grease with a clean cloth. During very cold,
damp weather more frequent application may be
required. (See ªRecommended Fluids and Lubricantsº in
the Index.)
Manual Transmission Check
Check the transmission fluid level; add if needed. See
ªManual Transmission Fluidº in the Index. Check for
leaks. A fluid loss may indicate a problem. Have the
system inspected and repaired if needed.
Automatic Transmission Check
Check the transmission fluid level; add if needed. See
ªAutomatic Transmission Fluidº in the Index. A fluid
loss may indicate a problem. Check the system and
repair if needed.

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8-6
Roadside Assistance
GMC's Roadside Assistance provides stranded owners
with over
-the-phone roadside repairs, location of the
nearest GMC dealer or the following special services:
Flat Tire Change: Installation of spare tire will be
covered at no charge (customer is responsible for repair
or replacement of tire).Fuel Delivery: Delivery of enough fuel for the customer
to get to the nearest service station (up to $4.00) will
be covered.
Jump Start: No
-start situations which require a battery
jump start will be covered at no charge.
Lock Out: Replacement keys or locksmith service will
be covered at no charge if you are unable to gain entry
into your vehicle. Delivery of the replacement key will
be covered at no charge within 10 miles (16 km).
Emergency Towing Service: Towing to the nearest
GMC dealer for warranty related disablements will
be covered.
Deluxe Trip Routing: Custom
-made, computerized
highlighted maps using the most direct or scenic route
are provided free of charge. Maps include points of
interest and a list of GMC dealers along the route. Also
included is a list of hotels along the route that are
discounted through affiliation with ªQuest
International.º Trip Routing is available through
Roadside Assistance by calling 1
-800-GMC-8782
(462-8782). Please be prepared to provide your Vehicle
Identification Number (VIN). Allow five working days
for fulfillment.

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8-7
Trip Interruption Assistance: GMC will reimburse any
reasonable trip interruption expenses (up to $500.00)
when directly associated with warranty disablement. Trip
Interruption service covers expenses such as meals and
overnight lodging if vehicle disablement occurs at least
150 miles (240 km) from your home or rental property.
Please Note: you will be required to obtain prior
approval from GMC Roadside Assistance and pay for
expenses at the time of disablement. Original receipts
should be submitted to GMC Roadside Assistance for
reimbursement. A service representative will provide
assistance when you call.
The Roadside Assistance services listed are available
to retail and retail lease customers operating 1999 GMC
light duty trucks for a period of 3 years/36,000 miles
(60 000 km). All services must be pre
-arranged by
GMC Roadside Assistance.
Over
-the-phone assistance, such as providing the name
of the closest dealer or minor technical advice, etc., is
available to all owner/operators of GMC trucks,
regardless of vehicle or mileage.
Just dial GMC Roadside Assistance at
1
-800-GMC-8782 (1-800-462-8782, Roadside
Assistance prompt) to reach a qualified representative
who can assist you.Your Roadside Assistance representative will ask for the
following information when your call is received:

Vehicle Identification Number (VIN)

Name and home address

Telephone number and location from which you
are calling

Location, license plate number and color of your
GMC truck

Mileage of vehicle and description of problem
Roadside Assistance is available 24 hours a day, 7 days
a week, 365 days a year, including weekends and
holidays. Should you have any questions about roadside
assistance, call the GMC Roadside Assistance Center or
contact your dealer.
Roadside Assistance is not part of or included in the
coverage provided by the New Vehicle Limited Warranty.
GMC reserves the right to make any changes or
discontinue the Roadside Assistance program at any
time without notification.
Canadian Roadside Assistance
Vehicles purchased in Canada have an extensive
Roadside Assistance program accessible from anywhere
in Canada or the United States. Please refer to the
separate brochure provided by the dealer or call
1
-800-268-6800 for emergency services.

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8-13
PUBLICATION FORM
NUMBEROrders will be mailed within 10 days of receipt. Please allow adequate time for postal
service. If further information is needed, write to the address shown below or call
1-800-551-4123. Material cannot be returned for credit without packing slip with return
information within 30 days of delivery. On returns, a re-stocking fee may be applied
against the original order. ORDER TOLL FREE
(NOTE: For Credit Card Holders Only)1-800-551-4123(Monday-Friday 8:00 AM ± 6:00 PM EST)
FAX Orders Only 1-313-865-5927
Service Manual
NOTE: Dealers and Companies please provide dealer or company name, and also the
name of the person to whose attention the shipment should be sent.
Mail completed order form to:
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P.O. Box 07130
Detroit, MI 48207
For purchases outside U.S.A. please write to the above address for quotation.
1999$90.00
1999
$50.00
1999
$20.00
1999
$15.00
TOTAL MATERIAL
Michigan Purchasers
U.S. Order Processing$6.00
Canadian Postage
GRAND TOTAL
add 6% sales tax
(See Note Below)
GM-GMC-ORD99 *(Prices are subject to change without notice and without incurring
obligation. Allow ample time for delivery.)Note to Canadian Customers: All listed prices are quoted in U.S. funds. Canadian residents
are to make checks payable in U.S. funds. To cover Canadian postage, add $11.50 plus the
U.S. order processing.
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