I rang the dealer today.
They said there was an issue with these alarms and Chrysler Technical are dealing with it. In the meantime they said press the lock button 4 times to deactivate the ultrasonic sensors. I thought I read in the book press lock 3 times but the extra press seems to do the job. Not only that on the 4th press the car 'chirps' to say the sensors are off.
So I don't have functioning ultrasonics but at least the neighbours get some peace and quiet!
Cheers!
BAC got a reaction from Yogitech1 in Alarm keeps going off.