2002 chevy van 3500 diesel

The van runs great it has 150,0000 miles on it. Bought it used. Recently it will stall, just cuts off. No warning and at no specific time. While I’m idling or decelerating or giving it gas. There are no error codes. Dealer does not know what it is. So before we just start changing parts has anyone had this problem???

Chevy dealership has checked it out 3 times and does not know what it is. Pressure, sensors no codes. they say the van is running great!