Immobilisation System Operation

Operation

Immobilisation System

The immobilisation system prevents unauthorised starting of the vehicle. The immobilisation ECU is a secure interface between the ECM which cannot be copied or by-passed.

Immobilisation ECU
The ECU ensures that the vehicle is in a safe condition to start the engine. On vehicles with an automatic transmission, the ECU prevents starter operation if the transmission selector lever is not in park or neutral. A feed from the automatic transmission solenoid (C0024) is connected to pin 3 on the immobilisation ECU. The feed is only present when the selector lever is in either park/neutral. If the selector lever is moved to any other position the feed to the immobilisation ECU is removed and engine cranking will be disabled.

When the ignition is switched to position 0 (off) and the key is removed from the switch, the immobilisation ECU becomes active and prevents unauthorised starter operation. Re-mobilisation is achieved only by insertion of a valid vehicle key into the ignition switch and turning the switch to position I (AUX).

Ignition Switch Transponder Coil and Key Transponder
The transponder coil is supplied with a modulated electric current from the immobilisation ECU. When the key transponder is within 2 cm (0.78 in) from the coil, with the ignition switch in the position I (AUX), an energy transfer from the coil to the transponder takes place, similar to the transformer principle, at a frequency of 125 kHz. The ECU de-modulates and decodes the received data and compares this with identification code data from the ECM. If the data is correct the ECU allows starter operation.

When the key is inserted in the ignition switch, communications between the transponder and the immobilisation ECU, via the transponder coil, occur as follows:
- A unique key identification number is passed to the ECU
- A random code is transmitted by the ECU to communicate with the key transponder
- An encrypted response to the random code is transmitted from the key transponder to the ECU.

Programming - Vehicles Up to VIN 242163
The immobilisation ECU is programmed with vehicle specific data during manufacture. The key transponders are supplied with the specific vehicle pre-programmed with the mechanical code for that vehicle's lockset. The mechanical code is read at the factory before the keys are programmed and the information is stored in a central database. The data is required to cut spare or replacement keys.

The ECU is programmed during manufacture with data to support up to ten keys. The programmed information is recorded against the VIN for that vehicle and stored in a central database.

Replacement or spare keys will be ordered and delivered to the dealer already programmed with the correct information specific to the particular vehicle and ready for use.

If a replacement immobilisation ECU is required it will be ordered and delivered to the dealer programmed with the original information stored during manufacture. The ECM will not require reprogramming because the replacement ECU will have the same identification code as before. The ECM and the EWS-3D immobilisation ECU will however need have their rolling code synchronised using T4.

If the ECM is replaced, the ECM will have to learn the identification code. This is achieved using T4. When the immobilisation ECU receives the correct diagnostic message it will transmit the identification code on a continual basis until the ignition is switched off. Simultaneously, the ECM also receives a diagnostic command to learn the new code.

Programming - Vehicles From VIN 242164
The immobilisation ECU is programmed with vehicle specific data by Land Rover during vehicle manufacture. This data is also stored in other ECU's on the vehicle. Non-sensitive data stored in the immobilisation ECU can be retrieved using T4.

The ECU is programmed during manufacture with data to support up to 30 keys which can be enabled with T4. Replacement or spare keys will be ordered and delivered to the dealer as a disabled key. The dealer will use the previously described 'Learn Blank/New Keys' procedure for enabling the new key. The key will be supplied with the correct key blade profile for the applicable vehicle lockset.

If a replacement immobilisation ECU is required it will be ordered and delivered to the dealer as a preprogrammed ECU. The ECM and the new immobilisation ECU will however need have their rolling code synchronised using T4.

If the ECM is replaced, the new ECM will have to learn the identification code. This is achieved using T4. When the immobilisation ECU receives the correct diagnostic message it will transmit the identification code on a continual basis until the ignition is switched to position 0 (off). Simultaneously, the ECM also receives a diagnostic command to learn the new code.

Starter Motor Protection
The immobilisation system incorporates a starter motor protection function. When the engine speed exceeds a predetermined value, a starter relay inside the immobilisation ECU is disabled. This relay is wired in series with the main starter motor solenoid and therefore when disabled it cuts off the power supply to the starter motor. This prevents damage to the starter motor being caused by a sticking ignition switch. The engine speed is derived from the instrument pack which converts the speed from a CAN bus signal into a pulsed signal compatible with the immobilisation ECU.

Diagnostics
A diagnostic socket allows the exchange of information between the immobilisation ECU and T4. The diagnostic socket is located in the driver's footwell and is constructed to ISO standard. A dedicated diagnostic bus is connected between the socket and the immobilisation ECU. The bus allows the retrieval of diagnostic information and programming of certain functions to be performed using T4.

The diagnostic bus protocol differs depending on the immobilisation system fitted to the vehicle as follows:
- for vehicles up to VIN 242163 (EWS3-D system) the immobilisation ECU uses DS2 protocol
- for vehicles from VIN 242164 the immobilisation ECU uses Keyword 2000* protocol.

The immobilisation ECU monitors all inputs and outputs and if a fault is detected, a code for that fault is stored in a fault log which can be retrieved using T4. The diagnostic interface is also used for synchronising a replacement ECM to the existing immobilisation ECU and for enabling or disabling new or current keys.