Wheels fitted with the tire low pressure sensor can be visually identified by a grey valve dust cap. All Ford non-tire pressure monitoring system wheels have a black valve dust cap.
The tire pressure monitoring system monitors pressure in each tire in a road wheel position. The tire pressure monitoring system monitors the pressure in each tire on the vehicle and provides the pressure information from all wheels to the driver through the instrument cluster menu.
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Radio frequency (RF) receiver
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Central junction box (CJB)
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Tire pressure monitoring system front antenna
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Tire low pressure sensor(s)
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Tire pressure monitoring system rear antenna
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.
The purpose of the tire pressure monitoring system is to assist the driver in maintaining the vehicles tire pressures at the optimum level in order to:
- Improve fuel consumption
- Maintain ride and handling characteristics
- Reduce the risk of tire failure – which may be caused by under-inflated tires
- Comply with legislation in relevant markets
- Aid the driver during the use of run-flat tires
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 Switch
The tire pressure monitoring system switch is a non-latching push button switch which is located in the center console switch pack.
The tire pressure monitoring system switch is used by the driver to set the required load conditions of the vehicle, normal load or high load. The tire pressure monitoring system switch is used to toggle between the two modes. The load conditions along with the vehicle speed conditions allow the tire pressure monitoring system to set the required target pressures for the vehicle. High speed vehicle conditions are automatically detected.
The tire pressure monitoring system switch has a status LED, located in the face of the tire pressure monitoring system switch, which informs the driver when the normal load or high load tire pressures are set. When normal load mode is set, the LED is illuminated. When high load mode is set, the LED is extinguished.
The status LED has two-stage illumination, providing day or night time illumination levels. The illumination level is determined by the tire pressure monitoring system module, based on data received through the CAN bus.
The tire pressure monitoring system switch is used to change between the modes as required. The ignition switch must be in position II. If the tire pressure monitoring system is in the normal load mode, pressing and holding the switch will change the target pressures to high load mode. The LED will be extinguished, the information and message center in the instrument cluster will display Tire Pressures High Load Condition for 5 seconds. This setting will remain until deselected by the driver.
To change from high load mode to normal load mode, the ignition switch must be in position II and the tire pressure monitoring system switch must be pressed and held. This will change the target tire pressures from high load mode to normal load mode. The tire pressure monitoring system switch LED will illuminate and the information and message center will display Tire Pressures Normal condition for 5 seconds.
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).
