Initial Inspection and Diagnostic Overview

Immobilizer - Immobilizer III On Board Diagnostic (OBD)

The electronic immobilizer consists of:
- an electronic control unit in the instrument cluster
- a warning light for anti-theft immobilizer sensor -K117- in the control module (in the speedometer)
- an adapted Engine Control Module (ECM)
- an induction coil at ignition lock
- and adapted ignition keys with electronics (transponder / response read memory).

Malfunction recognition and indication via warning light for anti-theft immobilizer sensor

When immobilizer is intact, the warning light for anti-theft immobilizer sensor -K117- lights up after ignition is switched on and switches off after approx. 3 seconds.

To indicate a malfunction during a system malfunction, the warning lamp blinks or remains constantly lit while ignition is switched on, if:
- adaptation of the ignition key was performed unsuccessfully.
- no transponder (response read memory) is available in ignition key.
- an unauthorized ignition key is being used.
- an unauthorized Engine Control Module (ECM) has been recognized.
- there is a functional disturbance in the induction coil (D2).
- there is a functional disturbance in the data wire.


The warning lamp for immobilizer does not light up after ignition is switched on:

- The control module for immobilizer recognized an authorized key.
- The control module for immobilizer did not recognize an incorrect Engine Control Module (ECM).
- The control module for immobilizer is busy performing the "Adapt ignition keys" procedure. No malfunctions occurred after key was adapted.

For troubleshooting, initiate On Board Diagnostic (OBD) and read out stored data using the VAG 1551 Scan Tool (ST).