User's Manual

Title : User manual of IM900 Immobilizer Spec. No. : N/A
Written by : SUNG HUN AHN Rev. No. : Revision A
Date :2007.11.07 Page : 4 / 10
Technical Center Automotive Electronics
3 System Function
3.1 Immobilizing Function
• Immobilizer at Accessory ON :
Turning on the Accessory triggers the Immobilizer to read out the transponder data and to compare
the red code with the valid key codes stored in the Immobilizer EEPROM. Until the end of
Transponder reading the Immobilizer is active state
• ECM at Accessory ON ECM :
After turning on the Accessory the ECM will control the engine in a normal way for starting and
running while waiting for a valid response message from the Immobilizer
• Immobilizer at Accessory OFF:
The inactive state of the Immobilizer (valid key / invalid key) ends with turning off the Accessory.
• ECM at Accessory OFF:
The immobilizing state of the ECM (released/blocked) ends with turning off the Accessory or
with removing the battery voltage.
3.2 Functions for Protection against Manipulation
3.2.1 Challenge and Response by SECT Algorithm
The Challenge and Response 4 byte data is calculated by the Immobilizer and ECM using a SECT
Algorithm provided by NXP.
The ciphered Challenge is transmitted by ECM through Gateway to Immobilizer in the serial message
communication in case of accessory was triggered. If user key is previously learned by learn coded key
procedure, immobilizer response with valid 4 byte data to the ECM through the Gateway. But without
authorized key is not learned by immobilizer invalid response is existed on the serial communication.