Antitheft and Alarm Systems: Description and Operation

IMMOBILIZER CONTROL SYSTEM

DESCRIPTION
There are two types of immobilizer functions available on the Body Control Module (BCM). The first is a "SMARTRA (SMART Transponder Antenna) type and the second is a "stand alone" type that will emulate the system known as the "SCE immobilizer". The hardware to support both types of immobilizer systems in the BCM is identical. The selection of immobilizer type within the BCM is effected by setting the appropriate EEPROM byte.

All communications between the BCM and the ECM (Engine Control Module) for the purposes of immobilization will be over the W-line.

The diagnostics communication for the SMARTRA system will be performed by communicating with the ECM on it's K-line. The ECM will then perform diagnostics on the BCM via the W-line.

At the time of Transponder validation, the BCM devotes 100 % processing power to the validation process in order to respond in the required time.

During transponder validation, other BCM functions may be influenced.

1. SMARTRA type immobilizer
The "SMARTRA" type immobilizer system is applied to the 2.0 Beta engine.

The immobilizer system consists of a passive challenge-response (mutual authentication) transponder inside the key head, a stand alone antenna, the BCM unit and the ECM. The BCM unit shall emulate the original SMARTRA immobilizer as closely as possible. In this document, the BCM emulating the original SMARTRA shall just be known as SMARTRA.

In the SMARTRA system, the immobilizer is contained within the ECM. The BCM shall provide the low-level routines and hardware necessary to communicate with the transponder.

2. Stand alone type immobilizer
The "Stand alone" type immobilizer system is applied to the 2.7 Delta engine.

The immobilizer system consists of a passive challenge-response (mutual authentication) transponder inside the key head, a stand alone antenna, the BCM unit and the ECM. The BCM unit shall emulate the original SCE type immobilizer to ECM protocol as closely as possible.

In the Stand alone immobilizer system, the immobilizer is contained within the BCM. The ECM shall request the BCM for permission to start the vehicle. The BCM shall perform the immobilization functions and reply "start" or "no start" permission to the ECM.




SYSTEM BLOCK DIAGRAM
The source of diagnostics commands for immobilizer equipped BCM's is different depending upon the type of immobilizer used. The diagnostics communication for the SMARTRA system will be performed by communicating with the ECM on its K-line.

In the case of a BCM that has an immobilizer, the detection of a tester being present will cause the K-line enable relay to close and the Diag pull up to be switched off. This mode of the diagnostics interface is called "Diagnostics" mode. This will then remain the case until the tester is disconnected. When the K-line enable relay is off and the diag pull up is enabled, this mode is called "immobilizer" mode.

Immobilizer Control System - Components (Part 1):

Immobilizer Control System - Components (Part 2):

COMPONENTS