Immobilizer Control System: Description: Notes
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.
- SMARTRA type immobilizer
The "SMARTRA" type immobilizer system is applied to the 2.00 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.
- Stand alone type immobilizer
The "Stand alone" type immobilizer system is applied to the 2.75 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.