Ford Galaxy / Ford S-MAX. Manual — part 49

During a blow-out, very rapid tire pressure is experienced. The tire pressure monitoring
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 reduce the likelihood of a tire blow-out occurring.

Principles of Operation

On driving off at a speed of more than 20 kph (12.5 mph) the central junction box (CJB)
sends a low-frequency (LF) signal to each tire pressure monitoring system antenna in turn.
Each antenna initiates its specific tire low pressure sensor. The corresponding tire low
pressure sensor responds after detecting its LF signal by sending a radio frequency (RF)
(315 MHz or 433 MHz depending on market) signal. These signals contain data which
corresponds to tire low pressure sensor identification, tire pressure, tire temperature and
vehicle acceleration information.

As each wheel responds to the LF signal from the CJB, it is assigned a position on the
vehicle and is monitored for the remainder of that drive cycle in that position.

The tire pressure monitoring system antennas operate in turn for 15 seconds in the
following order:

Left-hand front
Right-hand front
Right-hand rear
Left-hand rear

Each tire low pressure sensor responds in turn so that the CJB can establish the tire low
pressure sensor positions at the start of the drive cycle. This process is repeated up to 3
times but less if the tire low pressure sensor positions are already known in the CJB. This
process takes 3 to 4 minutes to complete. During this period the tire low pressure sensors
transmit at regular intervals once every 15 seconds. 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 park
mode.

The low tire pressure warning occurs at 25% + 35% deflation and consists of amber and
red warning lamp indicators and an appropriate message displayed in the information and
message center. The information and message center will also display additional
information about the position of the affected tire(s).

The tire pressure monitoring system enters the park mode after the vehicle speed has been
less than 20 km/h (12.5 mph) for 15 minutes. In park mode the tire low pressure sensors
transmit a coded signal to the CJB once every 13 hours. If the tire pressure decreases by
more than 0.06 bar (1 lbf/in²) within the 13 hours, the tire low pressure sensor will
transmit more often as the tire pressure is lost.

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 tire low pressure sensor is retained in
position by the tire valve nut to the wheel. The tire low pressure sensors transmit their RF

signals at either 315 MHz or 433 MHz dependent on market requirements.

The tire low pressure sensors periodically measure the tire pressure and temperature of the
air inside the respective tires. Pressure and temperature measurements are transmitted
periodically to the RF receiver on the vehicle.

The tire low pressure sensors are self-contained units.

The safety 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 installed and the tire low pressure sensor tightened to the correct
torque value.

It is strongly recommended that the valve seal and steel washer is replaced each time a tire
is changed to avoid a seal failure. The seal and washer must be replaced if the sensor is
removed. Removal of the sensor retaining nut must be regarded as sensor removal. The
valve cap must always be in place except when inflating, releasing pressure or checking
pressure.

The RF transmission from the tire low pressure sensor contains a unique identification code
in its transmission data so that the CJB can identify the tire on the vehicle. If a new tire low
pressure sensor is installed on a road wheel, the new tire low pressure sensor identification
will be learnt when the vehicle is first driven at a speed of more than 20 km/h (12.5 mph)
for 15 minutes.

It is strongly recommended that the valve seal and steel washer is replaced each time a tire
is changed to avoid a seal failure. The seal and washer must be replaced if the sensor is
removed. Removal of the sensor retaining nut must be regarded as sensor removal. The
valve cap must always be in place except when inflating, releasing pressure or checking
pressure.

Tire Pressure Monitoring System Antenna(s)

The tire pressure monitoring system has four tire pressure monitoring system antennas.
The tire pressure monitoring front antennas are located on top of the fender splash shield.
The tire pressure monitoring rear antennas are located on the rear bumper bracket. Each
tire pressure monitoring system antenna has a connector which connects with the body
wiring harness.

The tire pressure monitoring antenna is a passive, LF transmitter. Each tire pressure
monitoring system antenna is controlled by the CJB and provides an auto-location feature
to identify tire positions on the vehicle.

The CJB energizes each tire pressure monitoring 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 CJB through the
RF receiver. The CJB can then determine which tire low pressure sensor is transmitting and
its location on the vehicle.

CJB

The function of the CJB with the tire pressure monitoring system 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 CJB 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 CJB needs to identify the position of the tires on the vehicle and assign a
received tire low pressure sensor identification to a specific position on the vehicle (left-
hand front (FL), right-hand front (FR), left-hand rear (RL) or right-hand rear (RR)).

Tire location is carried out automatically by the CJB using an auto-location function. The
CJB automatically learns the position of tires on the vehicle if the tire low pressure sensors
or their positions are changed on the vehicle.

The CJB automatically detects, under normal conditions, the following:

One or more new tire low pressure sensors have been installed
One or more tire low pressure sensor has stopped transmitting
Signals from tire low pressure sensors that do not belong to the vehicle.

RF receiver

The RF receiver is part of the central locking system and is located above the headliner in
the vicinity of the overhead console.

The RF receiver receives tire pressure, temperature and vehicle acceleration information
from each tire low pressure sensor and interfaces with the CJB. The CJB then transmits the
appropriate messages to the instrument cluster through the controller area network (CAN)
bus.

The RF receiver also receives further information from each tire low pressure sensor
concerning wheel identification, mode status and the condition of the tire low pressure
sensor.

Instrument Cluster

The tire pressures on all 4 tires are displayed in the message center of the instrument
cluster, after being relayed by the CJB. Warnings are also visually displayed by the amber
and red warning indicators and a message is displayed in the information and message
center.

The warning indicators are driven by CAN messages from the CJB.

Tire Pressure Monitoring System Load Setting

The tire pressure monitoring system load setting switch is used by the driver to set the
required load conditions of the vehicle, normal load or high load.

Using the button located on the steering wheel right-hand side switch, select the
Information/Tires menu (located in the instrument cluster information and message
center).

To set the tire pressure monitoring system load setting required, select Set up/Tires menu.

The tire pressure monitoring system load setting can now be selected:

· Low load

· High load

To confirm the setting select OK.