Anti-Theft Immobilizer, on Board Diagnostic (OBD)
General Information
TT models from 09.00 production are equipped with Immobilizer Generation III.
Generation III has the same functionality as the previous version. However, in addition to the normal data exchange between the immobilizer control module and ignition key, Gen. III includes data exchange between the immobilizer control module and Engine Control Module (ECM).
Data exchange between the Immobilizer control module and ECM takes place over the vehicle CAN-Bus network.
NOTE:
- For Immobilizer III, the Engine Control Module (ECM) is actively incorporated into the evaluation and monitoring. The control module for immobilizer is integrated into the instrument cluster.
- For immobilizer III, the keys are marked with an inscribed "W". The code consists of a fixed code and a variable code portion.
Function
Immobilizer III consists of:
- an adapted control module for anti-theft immobilizer (integrated in instrument cluster)
- a warning light in instrument cluster
- an induction coil at ignition lock
- an adapted Engine Control Module (ECM)
- and adapted ignition keys with electronics (transponder).
The control module for anti-theft immobilizer is integrated in the instrument cluster, e.g. if control module is malfunctioning,instrument cluster must be replaced
The anti-theft immobilizer is a system for enabling/locking the Engine Control Module (ECM) via the CAN wire.
The transponder code consists of a fixed code and a variable code. This is different for every start procedure and therefore copy protection for the transponder.
Every immobilizer contains a different computational rule for the variable code that remains the same for its entire service life. adaptation of the vehicle key, the immobilizer writes this computational rule into the transponder and simultaneously learns code of the current key.
The fixed code identifies each individual key so that a key that is lost can be blocked from usage. Each time the ignition is switched on, the induction coil for immobilizer reads the transponder's fixed code and then the variable code and determines whether this key is authorized for vehicle start.
The warning lamp lights up briefly (max. 3 seconds) and then goes out when an authorized vehicle key is used.
When an unauthorized vehicle key is used or when a system malfunction occurs, the warning lamp blinks constantly during "on".
The electronic anti-theft immobilizer is capable of extensive On Board Diagnostic (OBD). If malfunctions occur in any of the system components, corresponding Diagnostic Trouble Codes (DTC) are stored in the DTC memory of the anti-theft immobilizer.
NOTE: All OBD program functions for anti-theft immobilizer must only be performed using VAS 5051 Vehicle Diagnostic Testing and Information System or VAS 5052 Vehicle Diagnostic and Service System.
WARNING: Anti-theft immobilizer OBD program functions described here must only be performed on a non-moving vehicle. DO NOT USE VAS 5051 during a road test.
Notes for use and adaptation of vehicle key
Engine will only start when an authorized vehicle key is used, i.e. on of the keys adapted to the immobilizer.
During adaptation of the vehicle keys, all vehicle keys, including replacement and emergency keys, must always be adapted to the immobilizer.
If new or extra vehicle keys are required, adaptation of all vehicle keys must be performed.
If adaptation cannot be performed for all vehicle keys, e.g. key lost during a trip, the customer must be informed that adaptation must eventually be performed for any and all vehicle keys.
Especially when a key has been lost, all vehicle keys should be re-adapted, since this will render the lost key unauthorized vehicle start.