Antitheft and Alarm Systems: Description and Operation
Online Engine Immobilizer 5 / Component Protection
The electronic engine immobilizer 5 protects the vehicle from unauthorized use. The 5th generation engine immobilizer used for the first time in the Panamera has been enhanced for the Cayenne with the introduction of component protection. In order to achieve a higher degree of security, the immobilizer is distributed over several components:
- Vehicle key with transponder
- Immobilizer master (front-end electronics)
- Electromechanical steering lock
- Engine control unit (DME)
- Anti-theft alarm system master (rear-end electronics)
Vehicle key
The vehicle key has a radio interface and a transponder interface. Using the radio interface, the user can actively operate the central locking system, i.e. the vehicle can be locked and unlocked.
A transponder interface is used for the function in the ignition lock. The data is exchanged between the key and the ignition lock via this interface. A battery is not required in the key for this interface. With the optional equipment "Porsche Entry & Drive", the key has an additional radio interface for near-field communication/ detection of approaching of the vehicle (125 kHz). The central locking (open/close function) responds via the normal radio interface (433 MHz).
Communication between the vehicle key and the immobilizer master is encrypted. Vehicle access with the remote control and access with "Porsche Entry & Drive" involve the transfer of 32 bits (4 bytes) of encrypted data. This produces approx. 4 million variants. To start the vehicle, 64 bits (8 bytes, remote control/Porsche Entry & Drive) of encrypted data is transferred for authentication of the key.
Electronic ignition lock
The ignition lock accommodates the vehicle key in the basic variant. The inserted vehicle key can be authenticated via the transponder interface in the ignition lock. To do this, the ignition lock converts the radio information into LIN signals for communication with the immobilizer master.
The ignition lock has three positions for operation:
- OFF
- Ignition (Terminal 15)
- Start engine (Terminal 50)
The vehicle key is reset from the "Start engine" position to the "Ignition" position automatically. The "Ignition" position has a detent so that the position can be uniquely identified at all times. The vehicle key can only be removed in the "OFF" position. For vehicles with Tiptronic transmission, the selector lever must be in the "P" position.
With the optional equipment "Porsche Entry & Drive", the ignition lock contains an operating element. The operating element remains in the ignition lock at all times. In this case, the valid key is authenticated via the radio interface between the vehicle key and immobilizer master.
Immobilizer master (front-end electronics)
The immobilizer master decides when to release the immobilizer. All components of the immobilizer must be authenticated by the master in this case. The immobilizer master functionality is integrated in the front-end electronics.
In addition to the driving authorization functions, this control unit contains:
- Exterior/interior light functions
- Central locking, Entry & Drive access function
- Terminal management (15, 30, 50)
- Control systems (e.g. electrically adjustable steering column, Servotronic, passenger compartment sensor)
Electromechanical steering column lock
The electromechanical steering lock serves to block the steering by mechanical means, in order to prevent unauthorized use of the vehicle. The electromechanical steering lock is installed in the steering system and can only be removed after dismantling the steering column. As a component of the electronic immobilizer, the electromechanical steering lock must be authenticated for release of the ignition by the immobilizer master.
Engine control unit (DME)
The engine control unit is authenticated by the immobilizer master via the CAN bus. Since the immobilizer master and the engine control unit cannot be on the same CAN bus, the messages are routed via a gateway. Only with positive authentication is the injection system released by the engine control unit as a requirement for engine operation.
Activating the engine immobilizer
The engine immobilizer is activated in the engine control unit by switching the ignition off. The engine control unit discards the internal release when the ignition is switched off and must obtain a new release from the immobilizer master the next time the ignition is switched on.
In the basic equipment, the electromechanical steering lock is activated by removing the vehicle key when the vehicle is stationary. The electromechanical steering lock blocks the steering system mechanically and discards the internal release of the engine immobilizer.
With the optional equipment "Porsche Entry & Drive", the electromechanical steering lock is activated after the ignition is switched off and the driver's door is opened, but no later than when locking up the vehicle. All variants prevent locking of the electromechanical steering lock when the ignition is on or the engine is running.
Rear-end electronics (anti-theft alarm system master)
The alarm system function is integrated into the rear-end electronics. The alarm system has no effect on driving authorization. However, the same processes are used to release the engine immobilizer and deactivate the alarm system.
Deactivation of the alarm system therefore also involves encryption, with data exchange via the CAN bus.
Component protection
Component protection is a new function on the Cayenne. In addition to the online engine immobilizer 5 functions, the gateway and airbag control unit functions are incorporated into the integrated system. If one of these control units is replaced, it must first be taught with the online teaching function. The component protection menu item must then be selected and the instructions followed.