The function of the immobilisation system is to prevent unauthorised starting of the vehicle. The system is controlled by the anti-theft alarm ECU in conjunction with the Engine Control Module (ECM) on Td5 vehicles, or the immobilisation ECU on 300 Tdi vehicles. Re-mobilisation is achieved by a transponder in the vehicle key, which is read by a transponder coil when the ignition switch is turned to the 'ignition' position.
Operation
Power Distribution
Feed from the positive battery terminal (C0192) is supplied to fuse 7, fusible link 1 and fusible link 5 of the under seat fuse box (C0632) on an N wire. Fuse 7 (C0574) provides a constant battery feed to the anti-theft alarm ECU (C1979 on LHD, C0061 on RHD) on a PN wire.
Fusible link 1 is connected in series with fusible link 2, which is also located in the under seat fuse box. Fusible link 2 (C0570) provides a constant battery feed to fuse 30 of the passenger compartment fuse box (C0595) on an NK wire. Fuse 30 (C0595) is connected to the engine immobilisation warning lamp (C1060) by a PN wire.
Fusible link 5 (C0570) provides a constant battery feed to the ignition switch (C1043 on LHD, C0028 on RHD) on an NW wire. When the ignition switch is turned to the 'ignition' position, current flows across the switch (C1732 on LHD, C0094 on RHD) to fuse 8 (Td5) or fuse 12 (300 Tdi) of the passenger compartment fuse box (C0580) on W wires. Fuse 8 (C0580) provides an ignition feed to the anti-theft alarm ECU (C1979 on LHD, C0061 on RHD) on a WG wire. Fuse 12 (C0580) provides an ignition feed to the immobilisation ECU (C0059) on a WG then B wire.
When the ignition switch is turned to the 'crank' position, current flows across the switch (C1732 on LHD, C0090 on RHD) to the starter relay (C0151) on a WR wire.
Transponder Coil
The transponder coil (C1318 on LHD, C0049 on RHD) is provided a battery value feed by the anti-theft alarm ECU (C1980 on LHD, C0057 on RHD) on an OP wire. The anti-theft alarm ECU (C1980 on LHD, C0057 on RHD) also provides the transponder coil (C1318 on LHD, C0049 on RHD) a pulsed feed on a OG wire. The transponder coil creates a magnetic field that excites a coil within the RF handset. This causes the RF handset to transmit a remobilisation code the anti-theft alarm ECU.
NOTE: The transponder coil is only energised when the ignition switch is turned to the 'ignition' position, and the engine is immobilised.
Anti-Theft Alarm ECU (Td5)
When the anti-theft alarm ECU (C1979 on LHD, C0061 on RHD) receives an ignition feed via fuse 8 of the passenger compartment fuse box (C0580), it provides the Engine Control Module (ECM) (C0658) a coded digital signal on an LGS wire. If the coded signal matches the one expected by the ECM, the ECM will allow the engine to be started. For more information on engine starting, refer to the Starting and Charging – Td5 section of this manual.
Anti-Theft Alarm ECU (300 Tdi)
When the anti-theft alarm ECU (C1979 on LHD, C0061 on RHD) receives an ignition feed via fuse 8 of the passenger compartment fuse box (C0580) , it provides the immobilisation ECU (C0059) a coded digital signal on an LGS then B wire. If the coded signal matches the one expected by the immobilisation ECU, the immobilisation ECU will allow the engine to be started. For more information on engine starting, refer to the Starting and Charging – 300 Tdi section of this manual.
Immobilisation Warning Lamp
Fuse 30 of the passenger compartment fuse box (C0595) provides a constant battery feed to the immobilisation warning lamp (C1061) on a PN wire. The anti-theft alarm ECU (C1980 on LHD, C0057 on RHD) also provides a feed to the warning lamp (C0233) on an O wire. As the potential difference across the bulb is 0 V, the lamp remains extinguished. To illuminate the lamp, the anti-theft alarm ECU withdraws the feed on the O wire and provides an earth path. By switching the feed/earth on and off, the immobilisation ECU can control the flashing sequence of the warning lamp.
Starter Relay
The starter relay coil (C0151) receives an 'engine crank' feed from the ignition switch (C1731 on LHD, C0090 on RHD) on a WR wire. When the vehicle is immobilised, the anti-theft alarm ECU (C1980 on LHD, C0057 on RHD) provides a feed to the other side of the relay coil (C0151) on a BO wire. When the anti-theft alarm ECU receives a valid re-mobilisation signal, it replaces the feed to the starter relay coil on the BO wire with an earth path. The energised starter relay is now able to provide a feed to either the starter motor (C0179) on an NR wire (Td5) or the immobilisation ECU (C0059) on an NR then B wire (300 Tdi).
For more details on starting, refer to the Starting and Charging – Td5 or Starting and Charging – 300 Tdi sections of this manual.
Immobilisation ECU – 300 Tdi Only
The immobilisation ECU (C0059) receives an ignition feed via fuse 12 of the passenger compartment fuse box (C0580) on a WG then B wire, and is earthed on a B wire.
When the ignition switch is turned to the 'ignition' position, the anti-theft alarm ECU (C1979 on LHD, C0061 on RHD) provides a coded digital signal to the immobilisation ECU (C0059) on a LGS then B wire. When the ignition switch is turned to the 'crank' position, the immobilisation ECU (C0059) receives a feed from the starter relay (C0151) on an NR then B wire. If the coded signal from the anti-theft alarm ECU has been accepted, the immobilisation ECU will provide a feed to the following on B wires:
Diagnostic Socket
The engine immobilisation system can be interrogated using TestBook via the diagnostic socket. The diagnostic socket (C0040) is connected to the anti-theft alarm ECU (C1979 on LHD, C0061 on RHD) by an LG wire.