Ldv convoy Imobiliser ?

I have a 2004 duratorque engined convoy tipper , lt never missed a beat until that little red light started flashing , after changing yellow relay , leaving batterie disconected , and various other things I tried . Towed it home twice I rang claybrow mobile tuning based in Skelmersdale Lancs 07774976946 . He plugged his computer in , removed the ring round the key barrel took the back off cleaned the blue gunk out scraped the terminals , put it back together job done! 15 mins .