Jaguar XJ (X350). Service manual — part 87
Tire Low Pressure Sensor
The tire pressure monitoring system uses ‘active’ tire low pressure sensors which are mounted on
each wheel, inside the tire cavity. The sensor is retained in position by the valve attachment to the
wheel. The tire low pressure sensors transmit their Radio Frequency (RF) signals at either 315 MHz or
433 MHz dependent on market requirements.
The tire low pressure sensor periodically measure the pressure and temperature of the air inside the
tire. Pressure and temperature measurements are transmitted periodically to the external RF
antenna on the vehicle.
The tire low pressure sensors are self-contained units which have no electrical connections into or
out of the tire low pressure sensor.
The care points detailed in 'Tire Changing' must be followed to avoid damage to the tire low pressure
sensor. If the tire low pressure sensor is removed, the nut, valve core, cap, seal and washer must also
be replaced and the tire low pressure sensor tightened to the correct torque value. It is also
recommended that the nut, valve core, cap, seal and washer are replaced at every tire change.
The RF transmission from the tire low pressure sensor contains a unique identification code in its
transmission data, so that the tire pressure monitoring system module can identify the tire on the
vehicle. If the tire low pressure sensor is replaced on a road wheel, the new sensor identification will
be learnt when the vehicle is first driven at a speed of more than 20 km/h (12.5 miles/h) for 15
minutes. If a new tire low pressure sensor is fitted to the spare wheel, the identification for that tire
low pressure sensor must be programmed into the tire pressure monitoring system module using a
Jaguar approved diagnostic tool or that wheel will not be monitored. The code is provided on a label
with the complete wheel and tire assembly when new and is also printed on the casing of each tire
low pressure sensor.
In order to conserve battery power, the tire pressure monitoring system module uses different
transmission rates when the wheel is stationary or moving. The wheel speed required to change
between the stationary and moving transmission rates is approximately 20 kph (12.5 mile/h).
Antenna
The antennas are located near the front of the front wheel arches, and the rear of the rear wheel
arches. The tire pressure monitoring system has four antennas. Each antenna has a connector which
connects with the body wiring harness.
The antenna is a passive, Low Frequency (LF) transmitter. Each antenna is controlled by the tire
pressure monitoring system module and provides an auto-location feature to identify tire positions
on the vehicle.
The tire pressure monitoring system module energizes each antenna in turn using LF drivers. The
corresponding tire low pressure sensor detects the resulting LF transmission and modifies the mode
status within the RF transmission. This data is received by the tire pressure monitoring system
module through the external RF antenna. The tire pressure monitoring system module can then
determine which sensor is transmitting and its location on the vehicle.
External Antenna
The tire pressure monitoring system external antenna is located at the rear of the vehicle and is
mounted between the spare wheel well and rear subframe.
www.
The unit receives tire pressure, temperature and acceleration readings from each tire and interfaces
with the tire pressure monitoring system module. The tire pressure monitoring system module then
transmits the appropriate messages to the instrument cluster.
The unit also receives further information from each tire pressure sensor concerning wheel
identification, mode status and the condition of the tire pressure sensor battery.
Instrument Cluster Indications
Item
Part Number
Description
1
Low tire pressure warning indicator
2
Secondary amber warning indicator
3
Message center
Warnings are displayed by the low tire pressure warning indicator, the secondary amber warning
indicator and a text message displayed in the message center.
The warning indicators are driven by controller area network (CAN) messages from the tire pressure
monitoring system module. The warning indicators are illuminated by the instrument cluster
software for three seconds when the ignition is switched to position II for a bulb check.
Note: If the vehicle is not fitted with the tire pressure monitoring system, the warning indicators will
not illuminate at any time.
System Operation
The tire low pressure sensor transmits by RF (315 MHz or 433 MHz depending on market) signal.
These signals contains data which corresponds to tire low pressure sensor identification, tire
pressure, tire temperature, acceleration and tire low pressure sensor mode.
Each time the vehicle is driven, the tire pressure monitoring system module activates each LF
antenna in turn. The corresponding tire low pressure sensor detects the LF signal and responds by
modifying the mode status within the RF transmission.
The system enters 'parking mode' after the vehicle speed has been less than 20 km/h (12.5 miles/h)
for 12 minutes. In parking mode the tire low pressure sensors transmit a coded signal to the tire
pressure monitoring system module once every 13 hours. If the tire pressure decreases by more than
0.06 bar (1 lbf/in²) the tire low pressure sensor will transmit more often as pressure is lost.
The spare tire sensor transmits a signal every 13 hours in the same manner as the road wheels when
in parking mode. If the tire pressure decreases by more than 0.06 bar (1 lbf/in²) the tire low pressure
sensor will transmit more often as pressure is lost.
As each wheel responds to the LF signal from the tire pressure monitoring system module, it is
assigned a position on the vehicle and is monitored for the remainder of that drive cycle in that
position.
When the vehicle has been parked for more than 15 minutes and then driven at a speed of more
than 20 km/h (12.5 miles/h), the antennas fire in turn for 6 seconds on all except North American
specification vehicles or for 18 seconds on North American specification only vehicles in the following
order:
•
Front left
•
Six second pause (for the tire pressure monitoring system module to detect a response from
the tire low pressure sensor)
•
Front right
•
Six second pause
•
Rear right
•
Six second pause
•
Rear left
•
Six second pause
Each tire low pressure sensor responds in turn so the tire pressure monitoring system module can
establish the tire low pressure sensor positions at the start of the drive cycle. This process is repeated
up to three times but less if the tire low pressure sensor positions are already known in the tire
pressure monitoring system module. This process is known as 'Auto Location' and takes three to four
minutes on all except North American specification vehicles and seven to eight minutes on North
American specification vehicles to complete. During this period the tire low pressure sensors
transmit at regular intervals, once every 5 seconds on all except North American specification
vehicles and once every 15 seconds on North American specification vehicles. For the remainder of
the drive cycle the tire low pressure sensors transmit once every 60 seconds or if a change in tire
pressure is sensed until the vehicle stops and the tire pressure monitoring system returns to parking
mode.
Once the wheel position is established, the antennas stop firing and do not fire again until the vehicle
has been parked for more than 15 minutes. The signal transmissions from each tire low pressure
sensor continue at one minute intervals whilst the vehicle is being driven. This transmission is to
monitor the tire pressure. The warning occurs at 25% deflation and comprises of message center
amber secondary warning light, the low tire pressure warning indicator and an appropriate message
displayed in the instrument cluster message center. The message center will also display additional
information about the position of the affected wheel(s).
www.
Нет комментариевНе стесняйтесь поделиться с нами вашим ценным мнением.
Текст