2001 GMC YUKON XL DENALI sensor

1-44 Servicing Your Air Bag-Equipped Vehicle
Air bags affect how your vehicle should be serviced.
There are parts of the air bag systems in several places
around your vehicle. Your dealer and the service manual
have information about servicing your vehicle and the
air bag systems. To purchase a service manual, see
ªService and Owner Publicationsº in the Index.
CAUTION:
For up to 10 minutes after the ignition key is
turned off and the battery is disconnected, an air
bag can still inflate during improper service. You
can be injured if you are close to an air bag when
it inflates. Avoid yellow connectors. They are
probably part of the air bag systems. Be sure to
follow proper service procedures, and make sure
the person performing work for you is qualified
to do so.
The air bag systems do not need regular maintenance.
Adding Equipment to Your Air
Bag-Equipped Vehicle
Q:If I add a push bumper or bicycle rack to the
front of my vehicle, will it keep the air bags
from working properly?
A:As long as the push bumper or bicycle rack is
attached to your vehicle so that the vehicle's basic
structure isn't changed, it's not likely to keep the
air bags from working properly in a crash.
Q:Is there anything I might add to the front or
sides of the vehicle that could keep the air bags
from working properly?
A:Yes. If you add things that change your vehicle's
frame, bumper system, front end or side sheet
metal or height, they may keep the air bag system
from working properly. Also, the air bag system
may not work properly if you relocate any of the
air bag sensors. If you have any questions about
this, you should contact Customer Assistance
before you modify your vehicle. The phone
numbers and addresses for Customer Assistance
are in Step Two of the Customer Satisfaction
Procedure in this manual. See ªCustomer
Satisfaction Procedureº in the Index.

2-37
Exterior Lamps
Your parking lamp and headlamp knob is on the driver's
side of your instrument panel.
Turn the knob clockwise to the parking lamps symbol to
manually turn on:

Parking Lamps

Sidemarker Lamps

Taillamps

License Plate Lamps

Instrument Panel LightsTurn the knob clockwise to the master lamps symbol to
turn on all the lamps listed as well as the headlamps.
Turn the knob all the way counterclockwise to turn
off your lamps and put the system into automatic
headlamp mode.
You can switch your headlamps from high to low beam
by pulling on the turn signal/high
-beam lever.
Automatic Headlamp System
When it is dark enough outside, your automatic
headlamp system will turn on your headlamps at the
normal brightness along with other lamps such as the
taillamps, sidemarker, parking lamps and the instrument
panel lights. The radio lights will also dim.
Your vehicle is equipped with a headlamp off delay,
which will keep the headlamps on for a short time after
the ignition is turned to OFF. For more information see
ªSecondary Information Center (SIC)º in the Index.
Your vehicle has a light sensor located on the top of
the instrument panel in the defroster grille. Be sure it
is not covered, or the system will be on whenever the
ignition is on.
The system may also turn on your headlamps when
driving through a parking garage, heavy overcast
weather or a tunnel. This is normal.

2-38
There is a delay in the transition between the daytime
and nighttime operation of the Daytime Running Lamps
(DRL) and the automatic headlamp systems so that
driving under bridges or bright overhead street lights
does not affect the system. The DRL and automatic
headlamp system will only be affected when the light
sensor sees a change in lighting lasting longer than
the delay.
To idle your vehicle with the automatic headlamp
system off, set the parking brake while the ignition is
off. Then start your vehicle. The automatic headlamp
system will stay off until you release the parking brake.
As with any vehicle, you should turn on the regular
headlamp system when you need it.
You may be able to turn off your automatic headlamp
system. See ªDaytime Running Lamps (DRL)º later in
this section for more information.
Lamps On Reminder
A reminder chime will sound when your headlamps or
parking lamps are manually turned on and your ignition
is in OFF, LOCK or ACCESSORY. To disable the
chime, turn the thumbwheel all the way down. In the
automatic mode, the headlamps turn off once the
ignition key is in OFF.
Puddle Lamps
Your vehicle is equipped with puddle lamps to help you
see the area near the base of the front doors when it is
dark out. The puddle lamps will illuminate when a door
is opened or when you press the UNLOCK button on the
keyless entry transmitter. The lamps will time out or
turn off once the engine is started.
You can program the puddle lamps not to come on if
you choose. See ªSecondary Information Centerº in the
Index for more information.
Daytime Running Lamps
Daytime Running Lamps (DRL) can make it easier for
others to see the front of your vehicle during the day.
DRL can be helpful in many different driving
conditions, but they can be especially helpful in the
short periods after dawn and before sunset. Fully
functional daytime running lamps are required on all
vehicles first sold in Canada.
The DRL system will come on when:

the ignition is on,

the headlamp knob is in automatic headlamp mode,

the automatic transmission is not in PARK (P),

the light sensor determines it is daytime and

the parking brake is released.

2-66
When one of the warning lights comes on and stays on
when you are driving, or when one of the gages shows
there may be a problem, check the section that tells you
what to do about it. Please follow this manual's advice.
Waiting to do repairs can be costly
-- and even
dangerous. So please get to know your warning lights
and gages. They're a big help.
Your vehicle also has a message center that works along
with the warning lights and gages. See ªMessage
Centerº in the Index.
Safety Belt Reminder Light
When the key is turned to RUN or START, a chime
will come on for about six seconds to remind people to
fasten their safety belts, unless the driver's safety belt is
already buckled.
The safety belt light will
also come on and stay
on for about 20 seconds,
then it will flash for
about 55 seconds.
If the driver's belt is already buckled, neither the chime
nor the light will come on.
Air Bag Readiness Light
There is an air bag readiness light on the instrument
panel, which shows the air bag symbol. The system
checks the air bag's electrical system for malfunctions.
The light tells you if there is an electrical problem. The
system check includes the air bag sensors, the air bag
modules, the wiring and the crash sensing and
diagnostic module. For more information on the air bag
system, see ªAir Bagº in the Index.
This light will come on
when you start your vehicle,
and it will flash for a few
seconds. Then the light
should go out. This means
the system is ready.
If the air bag readiness light stays on after you start the
vehicle or comes on when you are driving, your air bag
system may not work properly. Have your vehicle
serviced right away.

3-2
Comfort Controls
Electronic Climate Control System
Fan Knob
The knob on the left side of the electronic climate
control panel regulates the fan speed. To manually
increase airflow, move the knob clockwise. To manually
decrease airflow, move it counterclockwise.
OFF: If the knob is in OFF, outside air will still enter
the vehicle, and will be directed based on the position
of the mode knob.
AUTO: If the knob is in AUTO, the fan speed will vary
as the system maintains the selected temperature.When both the fan knob and mode knobs are in the
AUTO position, the system will then automatically
maintain the desired cabin temperature as selected
by the temperature knob. Manual operation is
also available.
Temperature Knob
The middle knob on the control panel lets you select
the desired air temperature in your vehicle. This knob
will allow you to adjust the interior air temperature
independent of the function knob setting. Move the
knob clockwise toward 82 for warmer air. Move the
knob counterclockwise toward 66 for cooler air. When
the system is set for automatic operation, sensors will
control the fan speed.
Full Hot: If you turn the temperature knob past 82
F
(28
C), the system will go into the ªfull hotº mode.
The system will remain at that maximum heating setting
and the fan will blow at the speed the fan knob is set to.
If the fan is in AUTO, it will run at full speed.
Full Cold: If you turn the temperature knob past 66
F
(19
C), the system will go into the ªfull coldº mode.
The system will remain at that maximum cooling setting
and the fan will blow at the speed the fan knob is set to.
If the fan is in AUTO, it will run at full speed.

3-3
Mode Knob - Automatic Operation
The right knob on the control panel allows you to
choose the direction of air delivery. When the system
is set in AUTO mode, sensors will control the air
delivery mode. Air will come primarily from the floor
or instrument panel outlets, with some air directed to
the windshield to prevent fogging.
When the system is in AUTO mode, the air conditioning
light will turn on, and the recirculation and outside air
lights turn off. With the system in full auto control
(both the fan and mode knobs in AUTO), you still
have the ability to override any function. However,
continually overriding the outside air or the A/C
compressor will limit the ability of the system to
cool the vehicle quickly.
If you push a button for a function which is not
available, the light next to that button will flash
three times to alert you that it's not available.
To find your comfort zone, start with the 74
F (23
C)
setting and allow about 20 minutes for the system to
adjust the temperature if necessary.With the automatic setting, the air conditioning
compressor automatically cycles when needed to cool
the air. In cold weather, when the system senses the need
for heat, the airflow will be directed out of the floor
outlets. As the interior temperature approaches a desired
setting, the fan speed will decrease. To maintain interior
comfort, the airflow will adjust between the instrument
panel air outlets and floor outlets. On bright sunny days
in cool weather, the airflow may come out of the air
conditioning and floor outlets (bi
-level mode) to
maintain comfort and prevent stuffiness.
To avoid blowing cold air in cold weather, the system
will delay turning on the fan until warm air is available.
The length of delay depends on the outside air
temperature, engine coolant temperature or the time
since the engine was last started. As the coolant warms
up, the fan speed will gradually increase and air will
flow from the heater outlets, with some airflow to
the windshield to prevent fogging under most
normal conditions.
Be careful not to put anything over the solar sensor
located around the center of the instrument panel.
This sensor is used by the automatic system to
regulate temperature.

6-65
Name Usage
O2 A Oxygen Sensors
O2 B Oxygen Sensors
LR PRK Left Rear Parking Lamps
RR DEFOG Rear Window Defogger,
Heated Mirrors
HDLP Headlamps (Relay)
TRL PRK Parking Lamps Trailer Wiring
PRIME Not Used
RT HDLP Right Headlamps
DRL Daytime Running Lamps (Relay)
HTD MIR Heated Mirrors
LT HDLP Left Headlamps
A/C Air Conditioning
AUX PWR Cigarette Lighter, Auxiliary
Power Outlets
SEO 2 Special Equipment Option Power,
Power Seats, Aux Roof Mnt Lamp
SEO 1 Special Equipment Option Power,
Aux Roof Mnt Lamp, Cell Phone
DRL Daytime Running Lamps
A/C A/C (Relay)
FOG LP Fog LampsName Usage
FOG LP Fog Lamps (Relay)
RADIO Audio System, Instrument Cluster,
Climate Control System
CIGAR Cigarette Lighter, Auxiliary
Power Outlets
RT TURN Right Turn Signals
BTSI Automatic Transmission Shift
Lock Control System
LT TURN Left Turn Signals
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, Headlamps