I am still having the same weird behavior of my Passo, that SILENT mode problem. No beep on indicators, reverse, key left in car beep... got it checked from the electrician recommended by Nabz90 he wasnt able to detect the fault even checked Toyota eastern motors (Gulistan-Johar).
I noted something very strange... whenever i leave my car in noon at under full sun light i mean in hot condition for 2 hours or so.... beeps work fine.. indicators, reverse beeps and everything but this works only in hot condition.
I think i have to live with this fault
or drive only in noon 
Someone plzz help