My car beeps when the engine is off!!

[HannahVegas]

I have had my Toyota Yaris for about 3 years now, it is a T reg and I've had no problems with it. It's not on finance and costs hardly anything to run due to the small engine size so I want to keep it despite its age. However, recently I noticed that there is a beeping under the hood. The really strange thing about this is the fact that it only happens when the engine is off? I've tried my best to define a time when it happens but there seems to be no pattern as to when it happens. For example, I thought that the weather could be affecting it somehow but even when its sunny it still beeps. Neither does it occur just as I park so it cant be due to the cooling process. The doors are all always locked so I don't believe it is a reminder of any sort. The beeps seem to work in patterns of 15 beeps, stops for approx 6 seconds then continues for another 15 beeps. The time in between the beeps can be shorter or longer. The beeps are not loud and therefore I don't think it they are linked to the alarm however they are quite irritaiting due to how common they are. If anyone could help me it would be very much apprieciated. Thanks.

[Robin-0291]

This may be the fault diagnosing system as some times they beep to tell engineers what the fault is check with a dealer they will not normally charge for this and will tell you over the phone