TIBURON(GK) >2005 > G 2.7 DOHC > Body Electrical System > Immobilizer System>Description and Operation  
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 withinthe 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 diagnosticson 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 2.0β 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 originalSMARTRA 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 communicatewith the transponder.
2.
Stand alone type immobilizer
The "Stand alone" type immobilizer system is applied to the 2.7δ 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 immobilizerto 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 immobilisation functions and reply "start"or no start" permission to the ECM.
SYSTEM BLOCK DIAGRAM

IMMOBILIZER STATES
1.
Engine Control Module (ECM) States
The ECM has three defined states. These are described below.
State
Description
Virgin State
The ECM is delivered to HMC in virgin state
There is no Vehicle Identification Number (VIN) stored in the ECM
It can only be in virgin state once
The ECM will allow starting on the second cycle of ignition
Virgin state is exited when a VIN has successfully been taught by the BCM
Learnt State
Engine start is possible only when the received VIN from the BCM matches that stored in the ECM
Neutral State
VIN has been deleted
Same as virgin state except engine starting not possible on the second cycle of ignition
Neutral state is entered if the BCM changes to neutral state

2.
Body Control Module (BCM) states
The Body Control Module (BCM) has three defined states. These are described below.
State
Description
Virgin State
The BCM is set to virgin state during manufacture
The BCM can be set back to virgin state by issuing an 'Initiate BCM' command
The diagnostics password is set to the default
No VIN is stored
Virgin state is exited only after the VIN been learned
Learnt State
The BCM contains a VIN
Neutral State
The BCM is set to neutral state by issuing a 'Teaching ECM' command
The purpose of the neutral state is to allow the ECM to be set to neutral state
The BCM neutral state expires 10 seconds after an ignition ON→OFF cycle

TEACHING PROCEDURES
THE USER PASSWORD CAN BE IN THE STATUS
LIMP HOME FUNCTION
The password and the pin code are not the same. Pin code is scanned from a bar code at the End Of Line (EOL). The passwordis a number chosen by the owner for the purposes of limp starting.