1st disconnect the siren & see if it goes away then yes goto dealer given the sensitive side of the car this controls, for a siren given if its bit pants I wouldnt scrimp on, I mean its only £80 ish for something that would last for many many years, mine lasted about 5-6 years, thats what £13.50 per year or so, its nothing huh & the new one is apparently even better as I fitted one & didnt make any noise after unless I set it of to test, lol.