The engine immobilizer system prevents the engine from starting and immobilizes the vehicle if a key other than the key registered for that vehicle is used in an attempt to start the engine after forced entry. The engine immobilizer system consists of the ignition key, the immobilizer ECU, and the engine-A/T-ECU. It works in the following way and has these functions:

1. After the ignition is switched on, the engine-A/T-ECU sends a control signal and transponder read to the immobilizer ECU.

2. When the immobilizer ECU receives the control signal from the engine-A/T-ECU, the immobilizer ECU supplies a current and sends random number data to the transponder in the ignition key.

3. The transponder uses the random number data to derive an ID code, which is sent to the immobilizer ECU.

4. The immobilizer ECU compares the ID code that was sent with pre-registered ID codes, and if it matches, a control signal approving ignition is sent to the engine-A/T-ECU. If the ID code does not match (in the case of counterfeit ignition keys, for example), the immobilizer ECU sends a control signal denying ignition to the engine-A/T-ECU, preventing the engine from starting.

5. The system is designed to be maintenance-free because the power source for the transponder is supplied by the immobilizer ECU. Two ignition keys are provided, and up to eight keys can be registered to one vehicle (one receiver) as needed. There are 4 billion possible combinations for the registered ID codes, and in addition, one part of the code is changed each time the key is switched on, which improves security by preventing theft using a copied ID code.

   

Diagnosis code No.	Diagnosis item
11	Transponder communication system or radio interference of encrypted code
12	Encrypted codes are not the same or are not registered