2009 JEEP GRAND CHEROKEE wheel size

•The ORC also turns on the Airbag Warning
Light for 2.5 to 8 seconds for a self-check
when the ignition is first turned on. After the
self-check, the Airbag Warning Light will
turn off. If the ORC detects a malfunction in any part
of the system, it turns on the Airbag Warning Light
either momentarily or continuously. A single chime
will sound if the light comes on again after initial start
up.
WARNING!
Ignoring the Airbag Warning Light in your instru-
ment panel could mean you won’t have the airbags to
protect you in a collision. If the light does not come
on, stays on after you start the vehicle, or if it comes
on as you drive, have the airbag system checked right
away.
•TheDriver and Passenger Airbag/Inflator Unitsare
located in the center of the steering wheel and the right
side of the instrument panel. When the ORC detects a
collision requiring the airbags, it signals the inflator
units. A large quantity of nontoxic gas is generated to
inflate the front airbags. Different airbag inflation rates
are possible, based on collision severity and occupant
size. The steering wheel hub trim cover and the upper
right side of the instrument panel separate and fold
out of the way as the bags inflate to their full size. The
bags fully inflate in about 50 to 70 milliseconds. This is
about half of the time it takes to blink your eyes. The
bags then quickly deflate while helping to restrain the
driver and front passenger.
The driver front airbag gas is vented through the vent
holes in the sides of the airbag. The passenger front
airbag gas is vented through the vent holes in the sides
of the airbag. In this way, the airbags do not interfere
with your control of the vehicle.
52 THINGS TO KNOW BEFORE STARTING YOUR VEHICLE

tires or wheels on your vehicle, to ensure that the
replacement or alternate tires and wheels allow the TPMS
to continue to function properly.
CAUTION!
The TPMS has been optimized for the original
equipment tires and wheels. TPMS pressures and
warning have been established for the tire size
equipped on your vehicle. Undesirable system opera-
tion or sensor damage may result when using re-
placement equipment that is not of the same size,
type, and/or style. Aftermarket wheels can cause
sensor damage. Do not use tire sealant from a can, or
balance beads if your vehicle is equipped with a
TPMS, as damage to the sensors may result.13. Temperature Gauge
The temperature gauge shows engine coolant tempera-
ture. Any reading within the normal range indicates that
the engine cooling system is operating satisfactorily.
The gauge pointer will likely indicate a higher tempera-
ture when driving in hot weather, up mountain grades,
or when towing a trailer. It should not be allowed to
exceed the upper limits of the normal operating range.
CAUTION!
Driving with a hot engine cooling system could
damage your vehicle. If the temperature gauge reads
“H” pull over and stop the vehicle. Idle the vehicle
with the air conditioner turned off until the pointer
drops back into the normal range. If the pointer
remains on the “H” and you hear continuous chimes,
turn the engine off immediately, and call an autho-
rized dealership for service.
UNDERSTANDING YOUR INSTRUMENT PANEL 189
4

Quadra-Trac IIOperating
Instructions/Precautions — If Equipped
The Quadra-Trac IItransfer case is fully automatic in the
normal driving 4WD HI mode. The Quadra-Trac II
transfer case provides three mode positions — 4WD HI,
NEUTRAL, and 4WD LOW.
This transfer case is fully automatic in the 4WD HI mode.
When additional traction is required, the 4WD LOW
position can be used to lock the front and rear driveshafts
together and force the front and rear wheels to rotate at
the same speed. The 4WD LOW position is intended for
loose, slippery road surfaces only. Driving in the 4WD
LOW position on dry hard surfaced roads may cause
increased tire wear and damage to driveline components.
When operating your vehicle in 4WD LOW, the engine
speed is approximately three times that of the 4WD HI
position at a given road speed. Take care not to overspeed
the engine and do not exceed 25 mph (40 km/h).Proper operation of four-wheel drive vehicles depends
on tires of equal size, type, and circumference on each
wheel. Any difference will adversely affect shifting and
cause damage to the transfer case.
Because four-wheel drive provides improved traction,
there is a tendency to exceed safe turning and stopping
speeds. Do not go faster than road conditions permit.
WARNING!
You or others could be injured if you leave the
vehicle unattended with the transfer case in the N
(Neutral) position without first fully engaging the
parking brake. The transfer case N (Neutral) position
disengages both the front and rear driveshafts from
the powertrain and will allow the vehicle to move
regardless of the transmission position. The parking
brake should always be applied when the driver is
not in the vehicle.
STARTING AND OPERATING 297
5

wheel lock-up and help avoid skidding on slippery
surfaces.
All vehicle wheels and tires must be the same size and
type, and tires must be properly inflated, to produce
accurate signals for the computer.
WARNING!
Significant over or under-inflation of tires or mixing
sizes of tires or wheels on the vehicle can lead to loss
of braking effectiveness.
The ABS conducts a low-speed self-test at about 12 mph
(20 km/h). If you have your foot lightly on the brake
while this test is occurring, you may feel slight pedal
movement. The movement can be more apparent on ice
and snow. This is normal.The ABS pump motor runs during the self-test at 12 mph
(20 km/h) and during an ABS stop. The pump motor
makes a low humming noise during operation, which is
normal.
WARNING!
•Pumping of the Anti-Lock Brakes will diminish
their effectiveness and may lead to an accident.
Pumping makes the stopping distance longer. Just
press firmly on your brake pedal when you need
to slow down or stop.
•The ABS cannot prevent the natural laws of phys-
ics from acting on the vehicle, nor can it increase
braking or steering efficiency beyond that af-
forded by the condition of the vehicle brakes and
tires or the traction afforded.
(Continued)
310 STARTING AND OPERATING

Keep dismounted tires in a cool, dry place with as little
exposure to light as possible. Protect tires from contact
with oil, grease, and gasoline.
Replacement Tires
The tires on your new vehicle provide a balance of many
characteristics. They should be inspected regularly for
wear and correct cold tire inflation pressure. The manu-
facturer strongly recommends that you use tires equiva-
lent to the originals in size, quality and performance
when replacement is needed. (Refer to the paragraph on
“Tread Wear Indicators”). Refer to the “Tire and Loading
Information” placard for the size designation of your
tires. The service description and load identification will
be found on the original equipment tire. Failure to use
equivalent replacement tires may adversely affect the
safety, handling, and ride of your vehicle. We recommend
that you contact your original equipment or an autho-
rized tire dealer with any questions you may have on tire
specifications or capability.
WARNING!
•Do not use a tire, wheel size or rating other than
that specified for your vehicle. Some combinations
of unapproved tires and wheels may change sus-
pension dimensions and performance characteris-
tics, resulting in changes to steering, handling, and
braking of your vehicle. This can cause unpredict-
able handling and stress to steering and suspen-
sion components. You could lose control and have
an accident resulting in serious injury or death.
Use only the tire and wheel sizes with load ratings
approved for your vehicle.
•Never use a tire with a smaller load index or
capacity than what was originally equipped on
your vehicle. Using a tire with a smaller load index
could result in tire overloading and failure. You
could lose control and have an accident.
(Continued)
342 STARTING AND OPERATING

For example, your vehicle has a recommended cold
(parked for more than three hours) tire pressure of 33 psi
(227 kPa). If the ambient temperature is 68°F (20°C) and
the measured tire pressure is 28 psi (193 kPa), a tempera-
ture drop to 20°F (-7°C) will decrease the tire pressure to
approximately 24 psi (165 kPa). This tire pressure is
sufficiently low enough to turn ON the Tire Pressure
Monitoring Telltale Light. Driving the vehicle may cause
the tire pressure to rise to approximately 28 psi (193 kPa),
but the Tire Pressure Monitoring Telltale Light will still
be ON. In this situation, the Tire Pressure Monitoring
Telltale Light will turn OFF only after the tires have been
inflated to the vehicle’s recommended cold tire pressure
value.CAUTION!
•The TPMS has been optimized for the original
equipment tires and wheels. TPMS pressures have
been established for the tire size equipped on your
vehicle. Undesirable system operation or sensor
damage may result when using replacement
equipment that is not of the same size, type, and/or
style. Aftermarket wheels can cause sensor dam-
age. Do not use aftermarket tire sealants or balance
beads if your vehicle is equipped with a TPMS, as
damage to the sensors may result.
•After inspecting or adjusting the tire pressure
always reinstall the valve stem cap. This will
prevent moisture and dirt from entering the valve
stem, which could damage the Tire Pressure Moni-
toring Sensor.
346 STARTING AND OPERATING

A tire pressure monitoring sensor is located in the spare
wheel, if the vehicle is equipped with a matching full-size
spare wheel and tire assembly. The matching full-size
spare tire can be used in place of any of the four road
tires. A low spare tire will not cause the Tire Pressure
Monitoring Telltale Light to illuminate, a warning mes-
sage to appear, or the chime to sound.
The Tire Pressure Monitoring Telltale Light will
illuminate in the instrument cluster, a “TIRE LOW
PRESSURE” message will display in the instru-
ment cluster for 60 seconds, and an audible chime will be
activated, when one or more of the four active road tire
pressures are low. Should this occur, you should stop as
soon as possible, check the inflation pressure of each tire
on your vehicle, and inflate each tire to the vehicle’s
recommended cold placard pressure value. The system
will automatically update and the Tire Pressure Monitor-
ing Telltale Light will extinguish, once the updated tirepressures have been received. The vehicle may need to be
driven for up to 20 minutes above 15 mph (24 km/h) to
receive this information.
The Tire Pressure Monitoring Telltale Light will flash on
and off for 75 seconds, and remain on solid when a
system fault is detected. In addition, a “CHECK TPM
SYSTEM” message will be displayed for 75 seconds when
a system fault is detected, and a chime will sound. If the
ignition key is cycled, this sequence will repeat, provid-
ing the system fault still exists. The Tire Pressure Moni-
toring Telltale Light will turn off when the fault condition
no longer exists. A system fault can occur by any of the
following:
1. Jamming due to electronic devices or driving next to
facilities emitting the same Radio Frequencies as the TPM
sensors.
2. Installing some form of aftermarket window tinting
that affects radio wave signals.
348 STARTING AND OPERATING

3. Lots of snow or ice around the wheels or wheel
housings.
4. Using tire chains on the vehicle.
5. Using wheels/tires not equipped with TPM sensors.
NOTE:
•If your vehicle is equipped with a matching full-size
spare wheel and tire assembly, it has a tire pressure
monitoring sensor, and can be monitored by the Tire
Pressure Monitoring System (TPMS). In the event that
the matching full-size spare tire is swapped with a low
pressure road tire, the next ignition key cycle will still
show the Tire Pressure Monitoring Telltale Light to be
ON, a “TIRE LOW PRESSURE” message will be
displayed in the instrument cluster for 60 seconds, and
a chime to sound. Driving the vehicle for up to
20 minutes above 15 mph (24 km/h) will turn OFF theTire Pressure Monitoring Telltale Light as long as none
of the road tires are below the low pressure warning
threshold.
•If your vehicle is not equipped with a matching
full-size spare wheel and tire assembly, it does not
have a tire pressure monitoring sensor in the spare tire.
The TPMS will not be able to monitor the tire pressure.
If you install the spare tire, in place of a road tire, that
has a pressure below the low-pressure warning limit,
upon the next ignition key cycle, a chime will sound, a
“TIRE LOW PRESSURE” message will be displayed in
the instrument cluster for 60 seconds, and the Tire
Pressure Monitoring Telltale Light will turn ON. After
driving the vehicle for up to 20 minutes above 15 mph
(25 km/h), the Tire Pressure Monitoring Telltale Light
will flash on and off for 75 seconds and then remain on
solid. In addition, a “CHECK TPM SYSTEM” message
will be displayed for 75 seconds. For each subsequent
ignition key cycle, a chime will sound, a “CHECK
STARTING AND OPERATING 349
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