Immobilizer Anti-Theft System

The immobilizer anti theft system requires diagnosis when it is not possible to start the engine If the no-start condition occurs because of the immobilizer system, a diagnostic trouble code (DTC) 53 should be set.
The immobilizer control unit monitors the detection and the reading of the ignition key. The self-test capacity is limited to those functions. Faults are communicated to a scan tool during diagnosis, but they are not stored in the immobilizer control unit's memory.
Unauthorized use of a scan tool could be a method of defeating the immobilizer anti-theft system, so certain scan tool procedures require the use of a password. The following functions are password protected:
- Coding of an additional key.
- Deleting all key codes.
- Deletion of the immobilizer identification (ID) code.
- Deletion of the electronic control module (ECM) ID code.

The following functions do not require a password:
- Reading an ignition key to determine if the transponder is working or if a key is authorized.
- Reading the immobilizer ID code to verily that it matches the ECM ID code.