7.4.3. Device and purpose of the antenna block of an immobilizer ("Smartra")

The transponder (it is built in a key)

Fig. 7.78. Transponder



At inclusion of ignition the frame antenna gives energy on the transponder which accumulates energy in the condenser.
As soon as delivery of energy from the frame antenna stops, the transponder gives confidential data, using the saved-up energy.
In the transponder the advanced algorithm of coding is used. When programming a key special data of the car which register in memory of the transponder are entered into the transponder. Record is disposable owing to what contents of memory of the transponder cannot be added or changed.

Antenna block of an immobilizer ("Smartra")

Fig. 7.79. Antenna immobilizer block



The Smartra block provides communication with the transponder which is built in the ignition key. Communication is carried out on a radio frequency 125 kHz. The Smartra block is installed on the ignition switch near a frame send-receive radio antenna.
The radio-frequency signal accepted by the frame antenna will be transformed by the Smartra block to messages of serial communication. The messages accepted from the control unit of the engine will be transformed to a radio-frequency signal which via the antenna is transmitted and the transponder of a key.
The Smartra block does not make check of correctness of recognition of the transponder and calculation of an algorithm of coding. It is only the advanced interface which will transform a flow of radio-frequency data from the transponder to a series of messages on the control unit of the engine and vice versa.

Control unit of the engine

Fig. 7.80. Control unit of the engine



The control unit of the engine checks the ignition key on a special algorithm of coding which is at the same time programmed in the transponder and the control unit of the engine. Start of the engine is possible only at coincidence of results of action of algorithms. Data of transponders of all operating keys of the car are stored in memory of the control unit of the engine.

Socket of a data line

Fig. 7.81. Socket of a data line



Diagnostic codes are read out by accession to the socket of the voltmeter or the Hi-Scan2 device.

Diagnostic unit

Fig. 7.82. Diagnostic unit



The device has the ICM functions ("Smartra"), ESM (the control unit of the engine), diagnostics and replacements of a key.

Emergency start by means of the diagnostic unit
If the control unit of the engine defines malfunction of the Smartra block or transponder, it will use function of emergency start of the engine in system of an immobilizer. Emergency start is possible only if the password of the user (4 figures) was earlier entered into memory of the control unit of the engine. The password is chosen the owner of the car and is entered at the service station. For emergency start the control unit of the engine will be unblocked on 30 with only provided that the control unit of the engine and the password of the user are in a state "is programmed" and the entered password of the user is correct. The engine can be started only during this time, on then start becomes impossible.
At issue of the wrong password of the user the control unit of the engine denies the request for start within one hour. Duration of this deviation cannot be reduced by shutdown of the rechargeable battery or any other actions. After connection of the battery the timer starts counting from scratch.

Emergency start by means of the ignition key
Function of emergency start can also be activated by means of the ignition key. At the same time the password of the user is issued for the control unit of the engine by the special sequence of inclusions and switching off of ignition. The control unit of the engine will be unblocked on 30 with only provided that the control unit and the password of the user are in a state also the entered password of the user correct "is programmed". The engine can be started only during this time, then start becomes impossible. After input of the new password the timer starts counting of the 30-second period from scratch.
After switching off of ignition the control unit of the engine is blocked after 8 pages. The following start requires repeated input of the password of the user.

Diagnostics of malfunctions of an immobilizer
The system of diagnostics controls:
– communication between the control unit of the engine and the Smartra block;
– operation of the Smartra block and transponder;
– the data which are stored in memory of the control unit of the engine relating to work of an immobilizer.
Errors of an immobilizer are divided into three groups, each of which includes four typical mistakes (malfunction of schemes, range schemes / rejection of characteristics, low level of a signal / high level). This classification of mistakes is presented on the provided table.

Replacement of the control unit of the engine and Smartra block
The faulty control unit of the engine is replaced with the "pure" or "neutral" block. At the same time all keys need to be programmed in the new block. The keys which are not programmed in the new block will not work (see the procedure of programming of keys). As it is impossible to change programming of transponders, special data of the car have to be left without change.
When replacing the Smartra block of any special procedures it is not required. Instead of the old Smartra block new is established. In this device it is not stored any data connected with the transponder.

Neutralization of the control unit of the engine
The control unit of the engine is brought to a "neutral" state by means of the test device.
The car key is inserted into the lock of ignition, and at inclusion of ignition its data register. The control unit of the engine requests special data of the car from the test device. Messages of communication are defined as "the neutral mode". After successful reception of data of the control unit of the engine passes into a neutral state.
The control unit of the engine remains blocked and does not provide the mode of emergency start and the "double inclusion of ignition" function.
Programming of keys is made as well as for the "pure" control unit of the engine. Owing to impossibility of change of programming of transponders special data of the car have to be left without change. For change of data it is necessary to have new keys with the pure transponder.