1999 GMC YUKON ignition

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4-26
Hard packed snow and ice offer the worst tire traction.
On these surfaces, it's very easy to lose control. On wet
ice, for example, the traction is so poor that you will
have difficulty accelerating. And if you do get moving,
poor steering and difficult braking can cause you to slide
out of control.
CAUTION:
Driving on frozen lakes, ponds or rivers can be
dangerous. Underwater springs, currents under
the ice, or sudden thaws can weaken the ice. Your
vehicle could fall through the ice and you and
your passengers could drown. Drive your vehicle
on safe surfaces only.
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.

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4-37
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.)

Keep your vehicle in good shape. Check all fluid
levels and also the brakes, tires, cooling system and
transmission. These parts can work hard on
mountain roads.

Know how to go down hills. The most important
thing to know is this: let your engine do some of the
slowing down. Shift to a lower gear when you go
down a steep or long hill.
CAUTION:
If you don't shift down, your brakes could
get so hot that they wouldn't work well. You
would then have poor braking or even none going
down a hill. You could crash. Shift down to let
your engine assist your brakes on a steep
downhill slope.
CAUTION:
Coasting downhill in NEUTRAL (N) or with the
ignition off is dangerous. Your brakes will have to
do all the work of slowing down. They could get so
hot that they wouldn't work well. You would then
have poor braking or even none going down a hill.
You could crash. Always have your engine running
and your vehicle in gear when you go downhill.

Know how to go uphill. You may want to shift down
to a lower gear. The lower gears help cool your engine
and transmission, and you can climb the hill better.

Stay in your own lane when driving on two
-lane
roads in hills or mountains. Don't swing wide or cut
across the center of the road. Drive at speeds that let
you stay in your own lane.

As you go over the top of a hill, be alert. There could be
something in your lane, like a stalled car or an accident.

You may see highway signs on mountains that warn of
special problems. Examples are long grades, passing or
no
-passing zones, a falling rocks area or winding
roads. Be alert to these and take appropriate action.

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4-43
Use the following procedure to correctly tow your
vehicle on all four wheels:
1. Firmly set the parking brake.
2. Place the transmission in PARK (P).
3. Securely attach the vehicle being towed to the
tow vehicle.
4. With the engine running, shift the transfer case to
NEUTRAL (N). See ªFour
-Wheel Driveº in the
Index for the proper procedure to select the neutral
position for your vehicle.
5. Release the parking brake only after the vehicle
being towed is firmly attached to the towing vehicle.
6. Turn the ignition to OFF. The OFF position unlocks the
steering column and reduces battery drain. Unlocking
the steering column will allow the proper movement of
the front wheels and tires during towing.
Loading Your Vehicle
The Certification/Tire label is found on the rear edge of
the driver's door.
The label shows the size of your original tires and the
inflation pressures needed to obtain the gross weight
capacity of your vehicle. This is called the Gross Vehicle
Weight Rating (GVWR). The GVWR includes the
weight of the vehicle, all occupants, fuel and cargo.

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5-4
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.
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) before setting the parking brake.
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. And 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.

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6-59
Fuse/Circuit
BreakerUsage
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)
20 PRNDL, Automatic Transmission,
Speedometer, Check Gages,
Warning Lights
21 Security/Steering
22 Auxiliary Power, Headlamp Delay
23 Rear Wiper, Rear Washer Pump
24 Front Axle, 4WD Indicator Lamp,
TP2 Relay
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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6-60
Name Circuits Protected
ECM
-B Fuel Pump, PCM/VCM
RR DEFOG Rear Window Defogger
IGN
-E Auxiliary Fan Relay Coil, A/C
Compressor Relay, Hot Fuel Module
FUEL SOL Not Used
GLOW PLUG Not UsedName Circuits Protected
HORN Horn, Underhood Lamp
AUX FAN Auxiliary Fan
ECM
-1 Injectors, PCM/VCM
HTD ST
-FR Heated Front Seats
A/C Air Conditioning
HTD MIR Heated Outside Mirrors
ENG
-1 Ignition Switch, EGR, Canister
Purge, EVRV Idle Coast Solenoid,
Heated O
2
HTD ST-RR Heated Rear Seats
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 Hi Blower and Rear Blower Relays
STOP/HAZ Stoplamps
HEATED
SEATSHeated Seats

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7-38
Ignition Transmission Lock Check
While parked, and with the parking brake set, try to turn
the ignition key to LOCK in each shift lever position.

The key should turn to LOCK only when the shift
lever is in PARK (P).

The key should come out only in LOCK.
Parking Brake and Automatic Transmission
PARK (P) Mechanism Check
CAUTION:
When you are doing this check, your vehicle
could begin to move. You or others could be
injured and property could be damaged. Make
sure there is room in front of your vehicle in case
it begins to roll. Be ready to apply the regular
brake at once should the vehicle begin to move.
Park on a fairly steep hill, with the vehicle facing
downhill. Keeping your foot on the regular brake, set the
parking brake.

To check the parking brake's holding ability:
With the engine running and transmission in
NEUTRAL (N), slowly remove foot pressure from
the regular brake pedal. Do this until the vehicle is
held by the parking brake only.

To check the PARK (P) mechanism's holding ability:
With the engine running, shift to PARK (P). Then
release all brakes.
Underbody Flushing Service
At least every spring, use plain water to flush any
corrosive materials from the underbody. Take care to
clean thoroughly any areas where mud and other debris
can collect.

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9-5
Gages
Engine Coolant Temperature 2-76 . . . . . . . . . . . . . . . . . . . .
Engine Oil Pressure 2-79 . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel 2-82 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Speedometer 2-71 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tachometer 2-71 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Voltmeter 2-74 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GAWR 4-44 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Gear Positions, Automatic Transmission 2-25 . . . . . . . . . . . . .
Glove Box 2-55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GM Mobility Program for Persons with Disabilities 8-5 . . . . .
GM Vehicle Care/Appearance Materials 6-54 . . . . . . . . . . . . .
Gross Axle Weight Rating 4-44 . . . . . . . . . . . . . . . . . . . . . . . .
Gross Vehicle Weight Rating 4-43 . . . . . . . . . . . . . . . . . . . . . .
Guide en Fran†ais ii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
GVWR 4
-43 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Halogen Bulbs 6-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hazard Warning Flashers 5-2 . . . . . . . . . . . . . . . . . . . . . . . . . .
Head Restraints 1-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Headlamp Delay 2-48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Headlamps 2-46, 6-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Bulb Replacement 6-34, 6-61 . . . . . . . . . . . . . . . . . . . . . . .
High/Low Beam Changer 2-41 . . . . . . . . . . . . . . . . . . . . . .
On Reminder 2-47 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wiring 6-56 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hearing Impaired, Customer Assistance 8-4 . . . . . . . . . . . . . .
Heated Front Seats 1-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Heated Rear Seats 1-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Heating 3-2, 3-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
High-Beam Headlamps 2-41 . . . . . . . . . . . . . . . . . . . . . . . . . .
Highway Hypnosis 4-36 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hill and Mountain Roads 4-36 . . . . . . . . . . . . . . . . . . . . . . . . .
Hitches, Trailer 4-48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hood, Checking Things Under 6
-8 . . . . . . . . . . . . . . . . . . . . .
Hood Release 6-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Horn 2-39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Hydroplaning 4-32 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Positions 2-21 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Ignition Transmission Lock Check 7-38 . . . . . . . . . . . . . . . . .
Inflation, Tire 6-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Inside Rearview Mirror 2-51 . . . . . . . . . . . . . . . . . . . . . . . . . .
Inspections 7-39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Brake System 7-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Drive Axle 7-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Engine Cooling System 7-39 . . . . . . . . . . . . . . . . . . . . . . . .
Exhaust System 7-39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Steering 7-39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Suspension 7-39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Throttle System 7-39 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transfer Case (Four-Wheel Drive) 7-40 . . . . . . . . . . . . . . .
Instrument Panel 2-68 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Brightness Control 2-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cleaning 6-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cluster 2-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuse Block 6-57 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interior Lamps 2-49 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jack, Tire 5-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Jump Starting 5-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Key Lock Cylinder Service 7-36 . . . . . . . . . . . . . . . . . . . . . .
Keyless Entry System 2-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Keys 2-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .