The normal reason for thee beeps is to tell you that it is in full EV mode if you are under 41 mph. However that should only happen when the screen switches to EV and the engine shuts off, not constantly.
The next reason is that the vehicle thinks you exited the vehicle with it in ready mode but the fob is with you.
The second one can happen if there is a cell phone close to the fob OR the fob has a weak battery or is inside something that blocks the signal, like one of the wallets or purses that has a lining that prevents ID theft.
Another possibility is a bad door latch switch that makes the car think a door is open.
There is also the possibility that it is something to do with the EV controller getting a false signal, for that you would need a factory scan tool and access to OEM programming options so you could test the system.
Monday, June 26th, 2017 AT 2:53 PM