I park my ZX EV on my drive and the direction happens to face the sun in the morning. This morning, as I know it is going to be hot, I put a white sheet over the screen and trapped it in the doors to keep it in place. I have done this before with no problem. I then lock the doors. No problem, they locked as normal and the mirrors folded in. After about ten minutes the car hooter suddenly started giving out a short bip about every half second. This continued for about 2 or 3 minutes then stopped by itself. I then checked that the car was locked and the boot was locked and they where. Has anybody else had this alarm signal?? If so, anybody know what caused it?