Jaguar XJ (X350). Service manual — part 86
Tread Wear Indicator
Tread wear indicators are molded into the bottom of the tread grooves across the width of the tire.
The tire must be renewed when tread wear indicators become visible at the surface of the tread, in
two or more adjacent tread grooves.
Note that tire tread depth and condition must comply with specific market legislations.
Tire Changing
Caution: When removing or installing a new tire care must be taken to make sure that the tire low
pressure sensor is not damaged. Make sure the tire bead is broken from the wheel rim 180 degrees
from the tire low pressure sensor. Failure to follow this instruction may cause damage to the tire low
pressure sensor.
Tire Pressure Monitoring
Visual Identification
Wheels fitted with the tire low pressure sensor can be visually identified by the external metal lock
nut and valve (1). All Jaguar non-tire pressure monitoring system wheels have a rubber valve fitted
(2).
The tire pressure monitoring system monitors pressure in each tire including the full size spare tire
(temporary-use spare wheels are not fitted with tire low pressure sensors and are consequently not
monitored).
Tire Pressure Monitoring System - Component Location
Item
Part Number
Description
1
Tire pressure monitoring system antenna
2
Tire low pressure sensor
3
Instrument cluster
4
External antenna
5
Tire pressure monitoring system module
The purpose of the tire pressure monitoring system is to assist the driver in maintaining the vehicle’s
tire pressures at the optimum level in order to:
•
improve fuel consumption
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•
maintain ride and handling characteristics
•
reduce the risk of rapid tire deflation – which may be caused by under inflated tires
•
comply with legislation in specific markets.
The tire pressure monitoring system measures the pressure in each of the tires on the vehicle and
issues warnings to the driver if any of the pressures deviate from a defined tolerance, which is
dependant on the vehicle market and the size and type of tire fitted.
Note: During a blow out a very rapid reduction in tire pressure is experienced. The system is not
intended to warn the driver of a blow out, since it is not possible to give the driver sufficient warning
that such an event is occurring, due to its short duration. The design of the tire pressure monitoring
system is to assist the driver in keeping the tires at the correct pressure, which may to reduce the
likelihood of a tire blow out occurring.
Tire Pressure Monitoring System Module
The tire pressure monitoring system module is located with the parking aid module in the luggage
compartment of the vehicle.
The tire pressure monitoring system module’s main function is to detect the following:
•
the tire pressure is below the recommended low tolerance value – under inflated tire
•
the position of the tire on the vehicle.
The tire pressure monitoring system module communicates with the vehicle instrument cluster to
provide the driver with appropriate warnings and also indicates the status/failure of tire pressure
monitoring system components.
Tire Location
Because of the requirement for different pressure targets and thresholds for the front and rear tires,
the tire pressure monitoring system module can identify the position of the tires on the vehicle, and
assign a received tire pressure sensor identification to a specific position on the vehicle (i.e. FL (front
left), FR (front right), RL (rear left) or RR (rear right)).
Tire location is performed automatically by the module using an auto-location function. This function
requires no manual intervention by the driver. The tire pressure monitoring system module can
automatically learn the position of tires on the vehicle if the tire pressure sensors or their positions
are changed on the vehicle.
The tire pressure monitoring system module can automatically detect, under normal conditions, the
following:
•
one or more tire pressure sensors have been replaced
•
one or more tire pressure sensor identifications are missing
•
one or more ‘alien’ identifications are being received, i.e. the module can reject
identifications from tire pressure sensors that do not belong to the vehicle
•
the spare tire and one of the tires in use on the vehicle have exchanged position on the
vehicle.
Spare Tire Identification
Depending on the vehicle specification, the spare tire may or may not be fitted with a tire pressure
sensor. Temporary-use spare wheels are not fitted with sensors and are consequently not
monitored.
If the spare tire is fitted with a tire pressure sensor, the tire pressure monitoring system module can
detect it, determine that it is the spare tire and monitor its pressure and issue warnings to the driver
accordingly. If the tire pressure monitoring system module does not detect a spare tire pressure
sensor, the tire pressure monitoring system module will not show a fault to the driver, however a
fault code will be stored in the tire pressure monitoring system module.
If the spare tire is being monitored and the driver replaces a flat road tire with the spare tire, the tire
pressure monitoring system module will not continually warn the driver that the original flat tire
(now in the spare position) is flat. This prevents distraction of the driver by constant pressure
warnings being issued. Warnings will only be displayed for 20 seconds after the ignition is switched
on.
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