Description and Operation

Description

The immobilizer system disables the vehicle if the correct ignition key is not used. In addition to the anti-theft systems currently available on the market, such as car alarms, the immobilizer system was developed to sharply reduce the number of vehicle thefts.

1. 1
   Transponder (TP) – IMMO ECU Communication

   

   TP Read Protocol

   1. After the ignition is turned on (or the MCU reset is released), IMMO ECU sends a challenge to the TP, and the serial number and signature are verified.
   2. If the response from the input transponder is incorrect, writing is repeated.
   3. When the response from the input transponder is correct, the data calculated by the encryption operation in the EEPROM program is compared with the data received from the TP. When the codes are identical, writing is complete. If the codes are not identical, input continues until the codes match.
   4. If the IMMO ECU EEPROM code is not programmed when the transponder is entered correctly (CRC check OK), input is complete.
   5. After ALL1 is activated (MCU reset released), the IMMO ECU reads the transponder code a maximum of 5 times.
   6. In the ALL1 ON & EMS locked state, when RECOGNITION is received, the TP is authenticated again.

      

2. 2
   Transponder / IMMO ECU / EMS Authentication

   

COMPONENT OPERATION

PCM (Powertrain Control Module)

1. The PCM (ECM) (A) verifies the ignition key using a special encryption algorithm that is programmed simultaneously into the transponder and the PCM (ECM). The engine will start only if the results are identical. Data for all registered transponders for the vehicle is stored in the PCM (ECM). The random number (EN code) between the EMS and the coded Smartra device is verified, and the EMS determines the validity of the coded key.

   

IMMOBILIZER CONTROL UNIT (A) The immobilizer communicates with the transponder built into the ignition key. This wireless communication is carried out in the radio frequency range (125 kHz). The immobilizer is installed behind the impact cushion near the centre bar. The radio frequency signal from the transponder, received by the antenna coil, is converted by the immobilizer into serial communication messages. Messages received from the PCM (ECM) are converted into FR signals and transmitted to the transponder through the frame antenna. The IMMOBILIZER does not perform transponder authentication or encryption algorithm calculation. This unit is simply an interface that converts the FR data rate of the transponder into communication sent to and from the PCM (ECM).

TRANSPONDER (built into keys) The transponder uses an advanced encryption algorithm. During the key learning procedure, the transponder is programmed with specific vehicle data. Vehicle-specific data is written to the transponder memory. This procedure is unique; therefore, the transponder contents can never be changed or replaced.

[Master Key Driver]

[Master Key Passenger]

ANTENNA COIL The antenna coil (A) performs the following functions.

• The antenna coil transmits energy to the transponder.
• The antenna coil receives the signal from the transponder.
• The antenna coil sends the transponder signal to the immobilizer. It is located directly in front of the steering column lock.