Hyundai Elantra: Immobilizer System / Description and operation

Hyundai Elantra (CN7) 2021-2025 Service Manual / Body Electrical System / Immobilizer System / Description and operation

Description

The immobilizer system will disable the vehicle unless the proper ignition key is used, in addition to the currently available anti-theft systems such as car alarms, the immobilizer system aims to drastically reduce the rate of auto theft.

Transponder (TP) – IMMO ECU Communication

TP Read Protocol

(1)	IMMO_ECU after IGN on(or CPU Reset cancellation) is sent Challenge to TP and confirmed Serial Number and Signature.

(2)	When response of input transponder is not correct, input is retry.

(3)	When response of input transponder is correct, The data that calculate Encryption operation in the EEPROM program compared with received data from TP. When Codes is same, input is finished. If the codes are not same, input are continued until when codes are same.

(4)	If IMMO_ECU EEPROM code is not programming, when correct transponder is inputted (CRC Check OK), input is finished.

(5)	After IGN1 on(CPU Reset cancellation), IMMO_ECU is reading the maximum 5times Transponder Code

(6)	In the IGN1 ON&EMS_state=Lock state, when received ANKNOWLEDGE, TP is re-authenticated

2.	Transponder / IMMO ECU / EMS authentication

Components Operations

PCM (Power Train Control Module)

The PCM (ECM) carries out a check of the ignition key using a special encryption algorithm, which is programmed into the transponder as well as the PCM (ECM) simultaneously. Only if the results are equal, the engine can be started. The data of all transponders, which are valid for the vehicle, are stored in the PCM (ECM).

ERN (Encrypted Randorm Number) value between EMS and encrypted smartra unit is checked and the validity of coded key is decided by EMS.

Encrypted Immobilizer Unit

The IMMOBILIZER carries out communication with the built-in transponder in the ignition key. This wireless communication runs on RF (Radio frequency of 125 kHz). The IMMOBILIZER is mounted behind of the crash pad close to center cross bar.

The RF signal from the transponder, received by the antenna coil, is converted into messages for serial communication by the IMMOBILIZER device. And, the received messages from the PCM (ECM) are converted into an RF signal, which is transmitted to the transponder by the antenna.

The IMMOBILIZER does not carry out the validity check of the transponder or the calculation of encryption algorithm. This device is only an advanced interface, which converts the RF data flow of the transponder into serial communication to the PCM (ECM) and vice versa.

Antenna Coil

The antenna coil (A) has the following functions.

–	The antenna coil supplies energy to the transponder.

–	The antenna coil receives signal from the transponder.

–	The antenna coil sends transponder signal to the IMMOBILIZER. It is located directly in front of the steering handle lock.

Immobilizer System

Repair procedures

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Function malfunction and limitations

Function malfunction

When High Beam Assist is not working properly, the ‘Check High Beam Assist (HBA) system’ or ‘Check HBA (High Beam Assist) system’ warning message will appear and warning light will illuminate on the cluster. Take your vehicle to an authorized HYUNDAI dealer and have the function checked.