LR3/Disco 3
The TPMS system uses ‘active’ tire 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 structure. The sensors transmit their RF signals at either 315
MHz or 433 MHz dependent on market requirements.
The sensors periodically measure the pressure and temperature of the air inside the tire. Pressure and temperature
measurements are transmitted periodically to the RF receiver in the vehicle.
The tire pressure sensors are self-contained units which have no electrical connections into or out of the sensor.
The care points detailed in 'Tire Changing' in this chapter must be followed to avoid damage to the sensor. If the sensor is
replaced, the nut, seal and washer must also be replaced and the sensor tightened to the correct torque value as given in
the Service Repair manual.
The RF transmission from the sensor contains a unique identification code in its transmission data, so that the TPMS
module can identify the tire on the vehicle. If the sensor is replaced on a 'running' wheel, the new sensor identification will
be learnt when the vehicle is first driven at a speed of more than 12.5 mph (20 km/h) for 15 minutes. If a new sensor is
fitted to the spare wheel, the identification for that sensor must be programmed into the TPMS module using T4 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 sensor.
The replacement spare wheel may also be programmed to the vehicle by using it as a 'running' wheel for 12.5 mph (20
km/h) for 15 minutes, then replacing it to the spare wheel position.
In order to conserve battery power, the tire sensor 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 very low to
allow for the requirement for slow off-road driving.
TPMS Switch
NOTE:
The TPMS switch is a non-latching push button switch which is located in the center console switch pack, adjacent to the
hazard warning switch.
The TPMS switch is used by the driver to set the required target pressures for the vehicle, i.e. ‘normal load’ or ‘high load’.
The switch is used to toggle between the two modes.
The TPMS switch has a status LED, located in the face of the switch, which informs the driver when the ‘normal load’ or
‘high load’ 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 TPMS module, based on data received via the vehicle CAN interface.
The switch is used to change between the modes as required. The ignition switch must be in position II. If the TPMS 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 message center in the instrument cluster will flash '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 switch must be
pressed and held. This will change the target pressures from 'high load' mode to 'normal load' mode. The switch LED will
illuminate and the instrument cluster message center will display 'Tire Pressures Normal condition' for 5 seconds.
Instrument Cluster Indications
The TPMS switch is not fitted to NAS market vehicles. NAS vehicles do not have the option to select target
pressure modes.
