My alarm had a similar issue, but only activated on locking the car.
To cut a long story short and after a month of investigation and a visit to the Ford dealership.
It turned out to be a corroded pin 3 on the alarm module. This is the +12V supply from the main battery.
It was a manufacturing defect on the module, as the pin had not been tinned properly, causing the bare copper to corrode and become covered in verdigris (2015 Kuga). No signs of water ingress, even though the module is located in the wheel arch!
It is located in the front wing, above the liner. To access it you will need to remove the wheel, arch trim and inner liner. Not a small feat but do-able with time and patience.
If anyone needs further info, give me a shout.
It was a painful experience as the Ford dealership had it for a week on their diagnostics and couldn’t locate the fault, although they were very polite and professional.
Incidentally there is a 2.4 volt Nickel Metal Hydride battery inside the sealed module. Others have found this to be faulty and the cause of their problem.
Good, used modules can be bought from Ebay for £15. A new one from Ford is about £250.
Make sure you get the correct one as there are about four different models, all made by FoMoCo, France and fitted to a number of different cars - from Aston Martins to Jaguars, Volvo’s, Fords and probably many others.
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