Vehicle immobilisers are fitted as standard to modern cars and heavy
goods vehicles. Anti-theft mechanisms have become more sophisticated but
so have the methods employed by crooks. Nowadays once the thief has
gained access to a vehicle they will most likely use an electronic
deactivation tool which seeks to disable the immobiliser, once this has
been accomplished a blank transponder key/card can be used to start the
engine. In many cases communication with the immobiliser is made using
the OBD-II diagnostic connector.
Although the OBD-II protocol
itself does not support the immobiliser, the vehicle manufacturer is
free to use the interface as neces-sary for communication, either the
standard OBD-II signals or unused pins in the OBD-II connector (i.e.
those undefined in the OBD-II standard). Using one of these pathways the
immobiliser can usually be electronically disabled.
OBD Vehicle Protection Circuit Diagram
This
may be unsettling news for owners of expensive vehicles but when
professional car-thieves call, armed with the latest OBD-II hacking
equipment this simple low-cost low-tech solution may be all that you
need. The idea is ver y simple: if all connections to the OBD-II
connector are disconnected there is no possibility for any equipment, no
matter how sophisticated to gain access via the vehicle’s wiring.
The
OBD-II connector is usually locate d underneath the dashboard on the
passenger side; once its wiring loom has been identified a switch can be
inserted in line with the wires. The switch should be hidden away
some-where that is not obvious. In normal opera-tion you will be
protected if the vehicle is run with the wires to the socket
disconnected. Make sure however that you throw the switch reconnecting
the socket before you next take the vehicle along to a garage for
servicing or fault diagnosis.
The diagram shows the ISO K and
ISO L wires switched. To cover all bases it is wise for every wire to
the socket is made switchable except the two earth connections on pins 4
and 5 and the supply voltage on pin 16. Almost ever y vehicle
manufacturer has their own method of vehicle immobilisation, by
disconnecting every wire it ensures that no communication is possible
(even over the CAN bus). Now the innermost workings of your vehicle will
be safe from prying eyes. When a hacker plugs in a deactivation tool it
will power up as normal but probably report something like ‘protocol
unrecognised’ when any communication with the OBD port is attempted.
Author : Florian Schäffer - Copyright: Elektor
