Celia

What do you mean please by " changed siren" . Is that the alarm siren that goes off in the boot? Is it a £ 9.00 siren replacement Lexus part?

Just had CATLOC fitted to our Lexus CT after recent theft of catalytic converter in SW London. The thieves disabled alarm by cutting lead to horn through grill.. see pic of lead poking out of grill .. Is there a way to stop this - as alarm is the first first line of defence?