L322 Range Rover System Description and Operation
DRIVING AIDS
DESCRIPTION AND OPERATION 86-10-15
Operation
Initialisation
Initialisation is required so that the TPM ECU can learn the identity and position of the tyre sensors, and the nominal
pressures of the associated tyres. Initialisation is invoked by pressing and holding the reset switch, with the ignition
switch in position II and the engine off, until the SET TYRE PRESSURE (software version 9) or TYRE PRESSURE
SET (software version 10) message appears in the instrument pack message centre (approximately 4 seconds).
When the switch is first pressed, a series of asterisks appear in the message centre to confirm that the TPM ECU has
received the switch input. The SET TYRE PRESSURE/ TYRE PRESSURE SET message goes off after
approximately 16 seconds.
Initialisation is required after:
l
A tyre pressure has been adjusted
l
A wheel has changed position, e.g. swapped axles or the spare installed as a road wheel
l
A replacement tyre sensor or TPM ECU has been installed.
WARNING: Without initialisation tyre pressure monitoring is inaccurate and may not be able to detect an
unsafe tyre pressure. Inflating tyres to the recommended pressure for the current vehicle load and driving
conditions remains the responsibility of the driver.
NOTE: Vehicles are built with tyres at storage pressure. At PDI tyres must be inflated to the correct pressure and,
where fitted, the TPM system must be initialised.
After being invoked by the reset switch, initialisation occurs during the subsequent drive cycle(s) when the vehicle is
travelling at more than 2.5 mph (4 km/h). At lower speeds initialisation is suspended, then automatically continued
when the speed goes above 2.5 mph (4 km/h) again. Initialisation is a transparent process that takes from 15 to 30
minutes and is conducted while driving to reduce the possibility of interference from outside RF transmission sources.
During the initialisation process, if the TPM ECU incorporates software version 10, the TYRE CONTROL INACTIVE
message is displayed in the instrument pack message centre. If the TPM ECU incorporates software version 9, no
message is displayed.
There are two phases to the initialisation process: a wheel identification phase and a wheel position phase.
Wheel Identification
Wheel identification takes from 4 to 8 minutes. When the TPM ECU has received more than three transmissions from
the same tyre sensor, it recognises that tyre sensor as belonging to the vehicle. The TPM ECU records up to five tyre
sensor identities and their current pressure and temperature readings. From the pressure and temperature of each
tyre, the TPM ECU calculates a theoretical pressure at 20
°
C (68
°
F) and uses this as the nominal pressure for
monitoring.
The TPM ECU then begins to monitor the tyres for pressure loss and continues the initialisation process to determine
the wheel position of the individual tyre sensors.
