OK I have to own up to having a left hand drive model where the 5AS is mounted on the inside of the bulkhead near the drivers left knee. UK models I assume are mounted in a mirrored set up near the drivers right knee. Easy to identify by the pink cable going to nowhere which is actually the antenna.
The 5AS is a Lucas Immobiliser which can lock out certain ECU functions. It is enabled or disabled by using a “Plip” key. When enabled a LED indicator on the dashboard will flash.
Well its pretty obvious what its for, to stop your car getting nicked! Lucas improved the receiver in 1995 earlier models being somewhat intermittent in the lock/unlock operation. You can identify in which the unit was manufactured as it is printed on one of the white labels in the form Week No./Year in my case 17/99. In most European countries the radio carrier frequency used is 433.92MHz (France 224.5GHz, Italy 315.0MHz). The unit is coded with a four number coding (0-15) the so called EKA and you would need special equipment to find out what it is. If you loose +12v power you will need to re-synchronise the Plip key with the 5AS (see here).
|1|| ||Ignition Switch On (+12V)||DC||Ignition Switch on Position|
|2|| ||Dashboard Ground||DC||Dashboard Ground|
|4|| ||Dashboard Ground||DC||Dashboard Ground|
|9|| ||Immobiliser Logic (4 Digit Code)||TTL||Loom Connector1 Pin 13|
|16|| ||Diagnostic I/O (1)||TTL||Diagnostic Connector Pin 3|
|17|| ||Immobiliser LED Drive||DC||Dashboard LED|
|19|| ||Dashboard Ground||DC||Dashboard Ground|
|24|| ||Diagnostic I/O (2)||TTL||Diagnostic Connector Pin 1|
|26|| ||Battery direct +12V||DC||Battery +12V|