Detection Of Unlock Request

When a VALID key is inserted in the ignition switch, the immobilization ECU transmits a VALID KEY IN LOCK message on the K-bus. The steering lock ECU receives this message and starts the unlocking process of operating the steering lock motor to disengage the locking bolt.

The immobilization ECU goes into sleep mode 60 seconds after the vehicle is unlocked and a key is not inserted in the ignition switch. When the key is subsequently inserted in the ignition switch and rotated, the rotation is sensed by the Hall rotation sensor in the switch. Further rotation is prevented by the ignition switch lock solenoid actuator. The rotation sensor transmits a signal which is received by the steering lock ECU. This ECU sends a REQUEST IMMOBILIZATION ECU STATUS message on the K-bus which wakes the immobilization ECU. When the immobilization ECU confirms that a valid key is inserted, the ignition switch lock disengages and the steering lock ECU starts the unlocking process.

If the K-bus is inoperative, the unlocking operation is initiated by the rotation sensor signal. This is indicated to the driver through a delayed operation of the solenoid actuator preventing the key from being turned initially. The solenoid actuator is operated on a delay which will initially prevent the key from being turned. The solenoid actuator will unlock and allow the key to turn on the second attempt. A defect in the K-bus is detected if no response from the immobilization ECU is received after a 2.4 seconds period after the 'request immobilization ECU status' is sent.