L322 Range Rover System Description and Operation
SECURITY
86-5-22 DESCRIPTION AND OPERATION
Immobilisation System
When the vehicle is unlocked, with the driver's door lock or the remote handset, the BCU outputs a 'vehicle unlocked'
message on the K bus. The K bus message wakes the immobilisation ECU which energises the transponder coil
around the ignition switch. When the ignition key is close to, or inserted into, the ignition switch, the immobilisation
ECU reads the identity of the transponder. If the transponder/ignition key is valid, the immobilisation ECU outputs a
'valid key in ignition lock' message on the K bus.
When it detects the valid key in ignition lock message, the steering lock ECU disengages the steering column lock.
After disengaging the steering lock, provided it is also receiving a Park/Neutral signal from the Electronic Automatic
Transmission (EAT) ECU, the steering lock ECU sends a release signal to the immobilisation ECU. When the ignition
switch is turned from position 0 to position I, the immobilisation ECU interrogates the transponder for the password
and rolling code. If these are correct the immobilisation ECU sends the coded release signal to the ECM and, when
the ignition switch turns to position III, energises the starter solenoid to crank the engine. The immobilisation ECU also
writes a new rolling code to the transponder and verifies it to ensure it has been correctly received.
On petrol models, the immobilisation ECU energises the starter solenoid via the starter motor relay. The starter motor
relay is controlled by the ECM to provide the comfort starting function, which allows the engine to be started by a
momentary crank (position III) selection on the ignition switch. When the ignition switch turns to position III, the ECM
energises the starter motor relay, which energises the starter solenoid, until engine speed exceeds approximately 500
rev/min, or for 20 seconds, whichever occurs first.
If the vehicle is unlocked and the ignition key is not put into the ignition switch, the immobilisation ECU de-energises
the transponder coil and goes back into the sleep mode after approximately 60 seconds. When the ignition key is
subsequently put into the ignition switch and turned through 10
°
to 20
°
, the steering lock senses the movement and
sends a 'request electronic vehicle immobiliser status' message on the K bus. The message wakes the immobilisation
ECU, which energises the transponder coil and commences the transponder/ignition key identification and engine
mobilisation process as detailed above.
