Description And Operation: Description

WARNING: This page is about a different car, the 2015 Kia Forte5, 2015 Kia Forte Koup, and 2015 Kia Forte. However, it is still accessible from the selected car via links, so may be relevant.

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

Fig 1: Transponder - IMMO ECU Communication Diagram
Courtesy of KIA MOTORS AMERICA, INC.

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 5 times Transponder Code
6. In the IGN1 ON & EMS_state=Lock state, when received ANKNOWLEDGE, TP is re-authenticated
  
  Fig 2: Antenna Coil Unit Communication Diagram
  Courtesy of KIA MOTORS AMERICA, INC.
TP/IMMO ECU/EMS Authentication Flowchart

Fig 3: TP/IMMO ECU/EMS Authentication Flowchart
Courtesy of KIA MOTORS AMERICA, INC.