The automotive immobilizer system was designed to avoid the forced operation of the vehicle in robbery attempts ( Anti-Theft Automotive Immobilizers ). This system works with a code that is engraved on the key called Key ID.
Suppose the ID code transmitted by the key does not match the one pre-recorded in the ICM ( Immobilizer Control Module ). Then the ECM ( Electronic Control Module ) prevents injection, disabling the engine.
Therefore, each vehicle has a set of keys containing a unique ID code recorded in the ICM. Thus, in addition to other anti-theft systems, the immobilizer system drastically reduces the number of vehicle thefts.
First Steps working on Automotive Anti-Theft Immobilizers
In other articles, we have explained some parameters that the technician must consider when intervening in an immobilizer system.
The principle of operation is as follows: the signal transmitted by the key is captured by an antenna located around the main cylinder and sent to the immobilizer control module ( ICM ).
The Immobilizer Control Module analyzes and verifies the signal to determine if the signal matches the pre-registered code.
The Immobilizer Control Module transmits a message to the ECM (Engine Main Module). This is done so that fuel injection is allowed.
If the immobilizer Control Module does not verify the signal, the ECM will not produce fuel injection preventing the engine.
Siemens Immobilizer Case Study
In the SIEMENS 2.5 system, the signal is verified by the Automotive Immobilizer Control Module. Also, by the engine ECM, verify that this signal matches the VIN pre-registered in the ECM memory.
Communication between the ICM and the ECM is through the Kline, which is also used for communication between the ECM and the automotive scanner.
In this system, we can find a relay within the ICM, which is in charge of selecting the communication.
Components of Automotive Anti-Theft Immobilizers
Many electronic components are part of the INMO system, of which the first to be mentioned is the Transponder, which is incorporated in the head of the key (Plastic Body).
The antenna is responsible for generating the current to the transponder, which accumulates in a capacitor.
Once the antenna current ceases, the transponder transmits the KEY ID code using the accumulated current in the capacitor.
The antenna is another component of this system, which is not only responsible for generating current to the transponder but is also the one that receives the signal from the transponder. It also sends this signal to the ICM (INMO Module).
One of the most important components is the Immobilizer Control Module (ICM).
This is in charge of sending the current to the antenna, and then it is in charge of receiving and analyzing the signal from the antenna and then transmitting it to the ECM.
The ICM is also responsible for recording the ” S ” code, which comprises the ID code plus the password. If the remote control is mounted in the vehicle, the ICM receives the signal from the remote control and sends a signal to the ETACS (Total Automotive Electronics Control System) to open or close the doors.
Finally, we have the ECM, which when the ignition key is on, the engine ECM receives information from the ICM and allows fuel injection at the time of starting the engine.
Programmable Key Types on Anti-Theft Systems
In this system, we can find different types of keys; we have the ID Key, which is first used to record a single ID code in the ICM.
This ID code will then be engraved on the rest of the keys.
We have the Master Key, which must be the primary key once the ID code is engraved.
It has the letter ” M ” engraved on one side and is black.
And finally, we have the Sub Key, which is similar to the Master key, but it is impossible to open the glove compartment or the trunk. It has the letter ” S ” engraved on one side and is black (This is only one of the possible encodings usually used by KIA).
SIEMENS case: in this system, the password is used to record the rest of the keys if the ID key is unavailable.
The password and the ID code are also used to form the ” S ” code for the SIEMENS system.
This number only applies to the immobilizer and is used by the SIEMENS system to verify the ICM. To modify the codes recorded by the system, it is necessary to do this procedure with an automotive scanner of each brand.
Once the factory preset password has been changed, the ICM is now ready to record the new ID code.
Normally, the password has 4 digits between 0 and 9; if the customer does not remember the password after changing this number, the ICM will have to be replaced, and it will be necessary to record a new password.
An automotive scanner should be used to neutralize ICM and ECM for SIEMENS systems. The password reading function is not available.
Automotive Immobilizers and Auto Repair Shops
Working with Immobilizers has become very common in the automotive workshop union since it represents a very profitable item taking into account the Hours / Work concept; however, it must be seen from two perspectives:
1. Workshops that can carry out precise diagnoses on the immobilizer system and determine the real cause of the problem, but without reaching the programming procedure executed by a professional locksmith or by a technician specialized in immobilizers.
2. Specialized locksmith workshops that are experts in key programming but cannot relate failures in the electronic engine system.
We also found freelance technicians who troubleshoot immobilizers and purchased some programming equipment but do not apply procedures properly.
In conclusion, our responsibility is to abide by the procedures recommended by each manufacturer, and there are no ” Tricks, “only 3 pillars: Knowledge, Equipment, and Technical Information.