216504 - ANTI-THEFT SYSTEM

The anti-theft system is one of the devices that contributes to protecting the vehicle.

AIM

The anti-theft sytem prevents the engine from being started by unauthorized persons inhibiting the operation of the engine management control unit and the starter motor.

GENERAL DESCRIPTION

The dedicated system that protects the vehicle by preventing the engine from being started by unauthorized persons and inhibits the operation of the starter motor is known as the CODE system or immobilizer.In order to start the vehicle the user needs to be recognized by the vehicle.The device that grants the user access to the vehicle to start up the engine is the transponder.It is housed in the key-remote control and the Passive Entry system CID.The transponder emits a signal containing the user identification code: if it is an authorized transponder, the code is received by the NBC and sent to the functions dedicated to protecting the vehicle (immobilizer and alarm).If the vehicle is equipped with a Passive Entry system, the user is recognized whilst they are approaching the vehicle through the identification code given out by the CID. When the recognized user activates the handle to open the door, the alarm system is deactivated and they are allowed to enter the passenger compartment and start up the engine (key-less go).In the case of vehicles equipped with a traditional access/starting system, the transponder housed in the key-remote control only allows the engine to be switched on after the user has switched off the alarm system by pressing the special button on the remote control.

DESCRIPTION OF THE COMPONENTS

The CODE system consists of:

  • NBC
  • Aerial
  • Trasponder

NBC

As far as the anti-theft system is concerned, the NBC carries out the following basic functions:

  • deactivating the alarm system after recognizing an enabled transponder (for Passive Entry systems).
  • Giving off an electro-magnetic field for reading the transponder.
  • Sending the random code to the transponder.
  • Receiving the cryptographic code transmitted by the transponder.
  • Memorizing up to 8 transponders.
  • Memorizing the secret code.
  • Managing a list of 8 enabled identifiers.
  • Managing a list of 16 permanently disabled identifiers.

Aerial

This component has the function of receiving the signal transmitted by the transponder and sending it to the NBC.The aerial is electrifited by the NBC if a request to read the transponder is forwarded by the alarm system or by the immobilizer.Since the aerial needs to be as close as possible to the transponder (on account of electro-magnetic immunity, the limited range of the transponder and small dimensions) it is fastened coaxially to the ignition switch.

Trasponder

This component has the function of allowing the user to be recognized by the vehicle protection system.This task is carried out by sending a recognition system to the vehicle.The transponder contains:

  • SECRET CODE: cryptographic code (12 - 16 bytes) the same for each transponder in the same kit.
  • IDENTIFIER: 4 byte code which is different for each transponder produced.
  • The PROGRAMMING DATA for the secret code (3 bytes).

OPERATION OF THE SYSTEM

The anti-theft system works independently of the alarm system.In effect, even with the alarm switched off, the anti-theft system recognizes the user once again, before enabling the starting of the engine.Starting up the engine is the result of a series of events described below:

  • 1. DEACTIVATION OF THE ALARM SYSTEM: this operation is carried out by the user using the key-remote control (vehicle equipped with traditional access/starting system) or in accordance with the Passive Entry system instructions.
  • 2. USER IDENTIFICATION: if the vehicle is equipped with a Passive Entry system, the user is automatically recognized as they approach the vehicle. If the vehicle is not equipped with Passive Entry, the user should insert the ignition key in the ignition. At this point the transponder sends the aerial a presence signal following which the transponder is energized by the aerial by means of a magnetic field and it is interrogated. It responds by sending the aerial the secret code, encrypted. If the code is recognized as valid, the system prepares for the starting of the engine, otherwise it inhibits it.
  • STARTING THE ENGINE: this operation is common to both access/starting systems, in effect, the recognition code sent by the transponder is transmitted to the NBC (if the vehicle is equipped with a Passive Entry system then the clutch pedal must be pressed to allow starting). The NBC sends the starting enablement to the Steering Lock Node. The NBS enables the starter motor to receive the +50. At the same time, the NBC communicates with the Engine Control Node via the C-CAN. The NCM requests the NBC to check the fix code (starting authorization code); if the outcome of the check is positive, the engine is started, otherwise it is not.

IMMOBILIZER SYSTEM FAULT DIAGNOSIS

The immobilizer system can carry out the autodiagnosis of its components.The NBC is capable of identifying and memorizing the presence of the following malfunctions:

  • defective or missing transponder or secret code incorrect.
  • Transponder cancelled/disabled.
  • Transponder not recognized/not memorized.
  • Electrical connection for transponder aerial defective.