ignition GMC YUKON 2001 Repair Manual

4-39
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.

4-44
Recreational Vehicle Towing
There may be times when you want to tow your vehicle
behind another vehicle for use at your destination. Be
sure to use the proper towing equipment designed for
recreational vehicle towing. Follow the instructions for
the towing equipment.
When towing your vehicle, turn the ignition to OFF.
To prevent your battery from draining while towing,
remove the IGN 0 fuse from the instrument panel fuse
block. Be sure to reinstall the fuse when you reach
your destination. See ªFuses and Circuit Breakersº
in the Index.
Two-Wheel-Drive Vehicles
Tw o-wheel-drive vehicles, should not be towed
with all four wheels on the ground. Two
-wheel-drive
transmissions have no provisions for internal lubrication
while being towed. To properly tow these vehicles,
they should be placed on a platform trailer with all
four wheels off the ground.
In rare cases when it's unavoidable that a two
-wheel-drive
vehicle is to be towed with all four wheels on the ground,
the propeller shaft to axle yoke orientation should be
marked and the propeller shaft removed following the
applicable service manual removal/installation procedure.
Dust or dirt can enter the back of the transmission
through the opening created by removing the propeller
shaft if proper protection is not provided. Also, check
the transmission fluid level before driving the truck.

4-45 Four-Wheel-Drive Vehicles
CAUTION:
Shifting the transfer case into NEUTRAL can
cause your vehicle to roll even if the transmission
is in PARK (P), for an automatic transmission.
You or others could be injured. Make sure the
parking brake is firmly set before you shift the
transfer case into NEUTRAL.
Use the following procedure to tow your vehicle:
1. Firmly set the parking brake.
2. Shift the transmission to PARK (P).
3. Securely attach the vehicle being towed to the
tow vehicle.
4. 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 as long
as the IGN 0 fuse is removed. Unlocking the steering
column will allow the proper movement of the front
wheels and tires during towing.

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) and a manual transmission in NEUTRAL
before setting the parking brake. Put the transmission
in PARK (P). 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 positive (+) and
negative (
-) terminal locations on the other vehicle.
Your vehicle has a remote positive (+) jump starting
terminal and a remote negative (
-) jump starting
terminal. The remote positive (+) terminal is located
behind a red plastic cover near the driver's side of the
engine accessory drive bracket. To uncover the remote
positive (+) terminal, open the red plastic cover.
The remote negative (
-) terminal is located on the
engine accessory drive bracket. This is marked
ªGNDº on V8 engines.

5-22
Follow these instructions to lower the spare tire:
1. If the vehicle is equipped with a hoist lock, open the
spare tire lock cover on the bumper and use the
ignition key to remove the lock.
2. Assemble the wheel wrench and the two jack handle
extensions as shown. Insert the hoist end (open end)
of the extension through the hole in the rear bumper.
Be sure the hoist end of the extension connects into
the hoist shaft (the ribbed square end of the
extension is used to lower the spare tire).
3. Turn the wheel wrench counterclockwise to lower
the spare tire to the ground. Continue to turn the
wheel wrench until the spare tire can be pulled out
from under the vehicle. The wheel wrench has a
hook that allows you to pull the hoist cable towards
you, to assist in reaching the spare tire.
4. When the tire has been lowered, tilt the retainer at
the end of the cable so it can be pulled up through
the wheel opening.
5. Put the spare tire near the flat tire.
The tools you'll be using include the bottle jack (A),
the wheel blocks (B), the jack handle (C), the jack
handle extensions (D), and the wheel wrench (E).
If the flat tire is on the rear of the vehicle, you'll need
to use both jack handle extensions.

6-18
How to Reset the CHANGE ENGINE OIL Message
To reset the CHANGE ENGINE OIL message, turn the
ignition key to RUN with the engine off. Fully press
and release the accelerator pedal three times within five
seconds. If the CHANGE ENGINE OIL message flashes
for five seconds, the system is reset.
What to Do with Used Oil
Did you know that used engine oil contains certain
elements that may be unhealthy for your skin and could
even cause cancer? Don't let used oil stay on your skin
for very long. Clean your skin and nails with soap and
water, or a good hand cleaner. Wash or properly throw
away clothing or rags containing used engine oil.
See the manufacturer's warnings about the use and
disposal of oil products.
Used oil can be a real threat to the environment. If you
change your own oil, be sure to drain all free
-flowing
oil from the filter before disposal. Don't ever dispose of
oil by putting it in the trash, pouring it on the ground,
into sewers, or into streams or bodies of water. Instead,
recycle it by taking it to a place that collects used oil.
If you have a problem properly disposing of your used
oil, ask your dealer, a service station or a local recycling
center for help.
Engine Air Cleaner/Filter
The engine air cleaner/filter
assembly has an indicator
that lets you know when
the air filter is dirty and
needs to be serviced.
The indicator is located
on the air cleaner cover.
See ªOwner Checks and Servicesº in the Index to
determine when to check the indicator.
If the area inside the clear section of the indicator is
not completely yellow, no air filter service is required.
When the area inside the indicator is completely yellow,
past the red band, the words ªCHANGE FILTERº will
be highlighted. After changing the air filter, press the top
button on the indicator to reset it.

6-65
NAME Usage
CRUISE Cruise Control, Instrument Cluster
IGN 3 Ignition, Power Seats
4WD Four
-Wheel Drive System,
Auxiliary Battery
CRANK Starting System
INT PRK Parking Lamps, Sidemarker
Lamps, Interior Lamps
L DOOR Power Door Lock Relay
BRAKE Anti
-Lock Brake System
RR WIPER Rear Window Wiper
ILLUM Interior Lamps
SEAT Power Seat Circuit Breaker
TURN Exterior Lamps, Turn Signals,
Hazard Lamps
UNLOCK Power Door Locks
HTR A/C Climate Control System
WS WPR Windshield WipersNAME Usage
IGN 1 Ignition, Instrument Panel
AIR BAG Air Bag
MIR/LOCK Power Mirrors, Power Door Locks
DR LOCK Power Door Locks
PWR WDO Power Window Circuit Breaker
UNLOCK Power Door Lock Relay
IGN 0 PRND321 Display,
Odometer, PCM
SEO IGN Special Equipment
Option, Ignition, Onstar


SEO ACCY Special Equipment Option
Accessory, Cellular Telephone
RAP #1 Retained Accessory Power Relay
RDO I Audio System, Onstar


RAP #2 Rear Power Windows,
Sunroof, Radio, Onstar

6-69
Name Usage
STUD #1 Accessory Power/Trailer Wiring
Feed/Load Leveling
ABS Anti
-Lock Brakes
IGN A Ignition Switch
AIR A.I.R. System
RAP #1 Retained Accessory Power,
Power Mirrors, Power Door Locks,
Power Seat(s)
IGN B Ignition Switch
RAP #2 Retained Accessory Power/Rear
Power Windows, Sunroof, Radio
STUD #2 Accessory Power/Trailer Wiring
Brake Feed
TRL R TRN Right Turn Signal Trailer Wiring
TRL L TRN Left Turn Signal Trailer Wiring
IGN 1 Ignition, Fuel Controls
INJ B Ignition, Fuel Controls (Relay)
STARTER Starter (Relay)
PARK LP Parking LampsName Usage
FRT HVAC Climate Control System
STOP LP Exterior Lamps, Stoplamps
ECM I PCM
CHMSL Center High Mounted Stoplamp
VEH STOP Stoplamps, Cruise Control
TRL B/U Backup Lamps Trailer Wiring
INJ A Fuel Controls, Ignition
RR HVAC Rear HVAC
VEH B/U Vehicle Backup Lamps
ENG 1 Engine Controls, Canister Purge,
Fuel System
ETC Electronic Throttle Control
IGN E A/C Compressor Relay, Rear
Window Defogger, Daytime
Running Lamps, A.I.R. System
B/U LP Backup Lamps, Automatic
Transmission Shift Lock
Control System
ATC Automatic Transfer Case

6-71
Name Usage
FR PRK Front Parking Lamps,
Sidemarker Lamps
W/W PMP Windshield Washer Pump
HORN Horn (Relay)
IGN C Ignition Switch, Fuel Pump,
PRND321 Display, Crank
RDO AMP Radio Amplifier
HAZ LP Exterior Lamps, Hazard Lamps
EXP LPS Not Used
HORN Horn
CTSY LP Interior Lamps
RR WPR Rear Wipers
TBC Body Control Module, Remote
Keyless Entry, HeadlampsReplacement Bulbs*
Low-Beam Headlamps2 9006
High
-Beam Headlamps2 9005
Daytime Running Lamps (DRL) 2 3157KX
Front Marker Lamp 2 194
Front Parking and Turn Lamp 2 3157A
Rear Marker Lamp,
Taillamp and Stop Lamp2 3157
Rear Turn Lamp 2 3157
Back
-up Lamp2 3157
* For replacement bulbs not listed here, please consult
your dealer.

7-20
Automatic Transmission Shift Lock Control
System Check
CAUTION:
When you are doing this check, the vehicle could
move suddenly. If it does, you or others could be
injured. Follow the steps below.
1. Before you start, be sure you have enough room
around the vehicle. It should be parked on a
level surface.
2. Firmly apply the parking brake. See ªParking Brakeº
in the Index if necessary.
NOTE: Be ready to apply the regular brake
immediately if the vehicle begins to move.3. With the engine off, turn the key to the RUN
position, but don't start the engine. Without applying
the regular brake, try to move the shift lever out
of PARK (P) with normal effort. If the shift lever
moves out of PARK (P), your vehicle needs service.
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.