Component Location
General Description
The immobilizer system consists of a mutual authentication transponder inside the key head, a stand alone antenna, the BCM unit and the EMS. The BCM unit shall emulate the original immobilizer to EMS protocol as closely as possible.
In the Stand alone immobilizer system, the immobilizer is contained within the BCM. The EMS 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 EMS.
The communication between the BCM and EMS for the purposes of immobilization for the stand alone will be via the “W Line”.
DTC Description
This DTC is displayed "Engine Diagnostic Trouble Codes(DTC)".
This DTC indicates that Non Immobilizer ECM is equipped.(Non Immo ONLY)
DTC Detecting Condition
Item | Detecting Condition | Possible cause |
Enable Condition | ? IG ON | ? Faulty ECM |
Detecting Factors | ? Non immobilizer ECM is equipped. |
Schematic Diagram
Signal Waveform
ECM states
State | Description |
Virgin | ? The EMS is delivered to HMC in virgin state. ? There is no VIN* stored in the EMS. ? It can only be in Virgin state once. ? The EMS will allow starting on the second cycle of ignition. ? Virgin state is exited when a VIN has successfully been taught by the BCM. |
Learnt | ? Engine start is possible only when the received VIN from the BCM matches that stored in the EMS. |
Neutral | ? 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. |
Unknown | ? Except in the case of Virgin, Learn, Neutral states. |
*VIN(Vehicle Identification Number)
The Vehicle Identification Number(VIN) is used for the mutual authentication process between the EMS and BCM.
BCM(Body Control Module) states
State | Description |
Virgin | ? The BCM is set to Virgin state during manufacture. ? No VIN is stored. ? Virgin state is exited only after the VIN been learned and the Change to Learnt state command is received. |
Learnt | ? The BCM contains a VIN. |
Neutral | ? The purpose of the Neutral state is to allow the EMS to be set to Neutral state. ? The BCM Neutral state expires 10 seconds after an Ignition ON ? OFF cycle.(OFF=ACC or IG OFF) |
Locked | ? Locked by timer (After a certain number of incorrect user Password(4) or PIN Code(6) the ECM is locked for one hour and no inputs are accepted during this time) |
Key states
State | Description |
1 st 2 nd 3 rd 4 th | ? Number of the current transponder Key in the ignition. |
Not Check | ? It means that BCM cannot check the transponder data in the key cylinder - Communication circuit problem between BCM and Antenna coil - Virgin Transponder - Key with NO Transponder - More than 1(One) Transponder in the magnetic field - No Transponder in the magnetic field. - TP(Transponder) data blocked - TP data does not exist - TP data changed - TP Teaching error - Multiple TP data input |
Reference Data
Limp Home Mode
Limp home mode allows the driver to start a car when the immobilizer system has failed but BCM is still able to communicate with the EMS. Limp home mode is activated by "entering" the Limp Home Password of the system via activations of the ignition key. The timing for entering the password are shown blow in Figure2.
At the dealer, the new owner is asked to choose a PASSWORD which is 4 digit(2byte) in length.
The PASSWORD may also be placed directly in RAM using the scanner.
If the password is to be changed (for example if the user forgets the password), the dealer shall use the change Password menu on the scanner. The scanner will prompt the dealer to enter the 6 digit PIN code as obtained from the HMC database for the vehicle in question.
The PASSWORD and the PIN* code are not the same. The PASSWORD is a number chosen by the owner for the purposes of limp starting.
Limp home mode is not active when the BCM is in virgin state.
*PIN code : P Identification Number (Vehicle Secret Code)
Limp Home lockout timer
If the limp home password is incorrectly entered with the scanner, and the IGN is cycled from IGN OFF to IGN ON, a counter is incremented in the BCM. If this counter reaches 3, the BCM enters lock out mode.
During this time period, the BCM will not respond in Limp home mode if any password is entered via the scanner. If the power to the BCM is removed, when it is restored, the one hour timer will restart. Manual limp home mode (using the ignition key) is still possible though.
Limp home code entry is enabled after the key has been in the ignition position for greater than 5 seconds. If the ignition is turned on for longer than five seconds during the sequence, the sequence is then restarted and all timers cleared. If the ignition is off for longer than three seconds during the entry, the code number for that digit of the Limp Home Password is determined. If the ignition is turned off for longer than 10 seconds at any time before during or after code entry, all timers are cleared and limp home mode is deactivated. The number “0” is represented by 10 cycles of the ignition key.
For limp home mode, IGN OFF is defined as Ignition OFF position or ACC position.
Lock out mode
The BCM will enter lock out mode if the 9 byte seed in EEPROM does not match the 9 byte seed in RAM for three attempts of the following commands:
- Teach Transponder Keys to BCM
- Change Limp home Password
- Scantool entry of Limp home Password.
Upon activation, this mode locks out access to these commands for a period of 1 hour. This period cannot be reduced in any way ? even if diagnostics mode is terminated and then re-entered. If power is disconnected to the BCM, the 1 hour timer will be restarted upon restoration. This ensures that a potential car thief cannot easily crack the 9 byte security code, and hence steal the vehicle.
Things to remember before repairing
A repair case | Things to remember | Needed Item |
Registration(Missing all keys) | Register new keys with the PIN code | New keys |
Registration(additional new key) | Register new key with the PIN code(Be sure that keys which were already registered are need to re-register) | New key |
Replace New BCM | Register all keys which were already registered with the PIN code | New BCM |
Replace BCM registered another car | BCM registered another car can’t use | New BCM New Keys |
Replace New ECM | Do not need to register | New ECM |
Replace ECM registered another car | If key is turned IG ON, ECM registered another car is registered. Be sure that below things. 1.ECM registered another car must be neutralized before removing. 2.After neutralizing, Key must be turned IG ON(ON ? OFF ? ON) within 10 sec. | ECM registered another car |