Sigma M30 Siren help still needed please

[DAVID WILSON]

I have change the Battery in the siren and put the siren back on the car. I found a picture of the plug into the back of the alarm control box ,It is clearly a 4 pin plug/socket marked Siren however the siren has a plug that has only 3 pin plug  the colors  are ,Red ,Green, Yellow . The other color is Brown I have looked for some where to terminate it but not found anything  , The bonnet switch has 2 Black wires and there is a black going to car body earth .As you may have read in a previous post  a mouse had damaged the wires ,the repair was to insert wires to repair the damage color for color as it was easy to cut back the insulation to the good part of the harness .There was only one end of the Brown coming from controller .

The LED on the steering column is not lit at any time, The car locks/unlocks/starts and runs/drives and the immobilizer symbol is on when the car is locked .PLEASE CAN SOME ONE ADVISE WHERE THIS BROWN WIRE HAS TO GO ,OR AM I BEEN SENT A RED HERRING AND IT IS A SPARE AND NOT USED

Thank you for reading this 

David