Immobilization 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 immobilization ECU which energizes the transponder coil around the ignition switch. When the ignition key is close to, or inserted into, the ignition switch, the immobilization ECU reads the identity of the transponder. If the transponder/ignition key is valid, the immobilization 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 immobilization ECU. When the ignition switch is turned from position 0 to position I, the immobilization ECU interrogates the transponder for the password and rolling code. If these are correct the immobilization ECU sends the coded release signal to the ECM and, when the ignition switch turns to position III, energizes the starter solenoid to crank the engine. The immobilization ECU also writes a new rolling code to the transponder and verifies it to ensure it has been correctly received.

On petrol models, the immobilization ECU energizes 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 energizes the starter motor relay, which energizes 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 immobilization ECU de-energizes 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 immobilizer status' message on the K bus. The message wakes the immobilization ECU, which energizes the transponder coil and commences the transponder/ignition key identification and engine mobilization process as detailed above.