Hyundai Sonata LF Quiz
Body Electrical System

Description and Operation

In this manual: Body Electrical System
General Information — 9Engine Mechanical System — 90Engine Electrical System — 58Emission Control System — 24Engine Control System/Fuel System — 114Drive Shaft and Axle — 15Suspension System — 35Steering — 19Restraints — 50Brake System — 54Body (Interior and Exterior) — 213Body Electrical System — 241Heating, Ventilation, and Air Conditioning — 56DCT (Dual Clutch Transmission) System — 52
2steps
~12min
1/5difficulty
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Description

The immobilizer system disables the vehicle if the correct ignition key is not used. In addition to existing anti-theft systems, such as the car alarm, the immobilizer system is designed to sharply reduce the number of vehicle thefts.
  1. Transponder (TP) – Communication with IMMO ECU
    TP Read Protocol
    1. After IGN is turned on (or CPU reset is released), the IMMO_ECU sends a request to the TP and verifies the serial number and signature.
    2. When the transponder response is incorrect, the input is repeated.
    3. When the transponder response is correct, the data is used to calculate the encryption operation in the EEPROM program and compared with the data received from the TP. When the codes match, the input is complete. If the codes do not match, the input continues until the codes match.
    4. If the IMMO_ECU EEPROM code is not programmed when a correct transponder is entered (CRC check OK), the input is complete.
    5. After IGN1 is turned on (CPU reset released), the IMMO_ECU reads the transponder code a maximum of 5 times.
    6. In the IGN1 ON and EMS_state=Lock condition, when ACKNOWLEDGE is received, the TP is re-authenticated.
  2. Transponder / IMMO ECU / EMS Authentication

Components and Operation

PCM (Powertrain Control Module)
  1. The PCM (ECM) (A) verifies the ignition key using a special encryption algorithm that is programmed into the transponder and the PCM (ECM) simultaneously. The engine can only be started if the results are equal. Data for all transponders valid for the vehicle are stored in the PCM (ECM). The ERN (encrypted random number) value is exchanged between the EMS and the smart device, and the EMS verifies the validity of the encoded key.
Encrypted Immobilizer Unit (A): The IMMOBILIZER communicates with the transponder built into the ignition key. This wireless communication operates at radio frequency (125 kHz RF). The IMMOBILIZER is installed behind the protective cover next to the center crossbar. The RF signal from the transponder, received by the antenna coil, is converted into serial communication messages for the IMMOBILIZER unit. The messages received from the PCM (ECM) are converted into an RF signal, which is transmitted to the transponder through the antenna. The IMMOBILIZER does not perform transponder validity checks or encryption algorithm calculations. This unit is only an advanced interface that converts the RF data stream from the transponder into serial communication with the PCM (ECM) and vice versa.
Transponder (Built-in Key): The transponder has an advanced encryption algorithm. During the key learning procedure, the transponder is programmed with vehicle-specific data. The vehicle-specific data is written to the transponder memory. The write procedure is performed only once; therefore, the transponder contents can never be modified or changed.

[Master Folding Key]

[Master Key Assistant]

Antenna Coil: The antenna coil (A) performs the following functions.
  • The antenna coil supplies power 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.

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A quick Hyundai Sonata LF quiz: every answer comes with an explanation and a link to the manual page.