I bet you $100 that the problem is related to a bad ground or some wiring prob in the car. People spend SOOOO much money on sensors that dont need to be replaced, all because something simple like the terminals on the battery or ground connections are dirty.
BTW- if you have had a bunch of things replaced and it didnt fix the prob the you have been ripped by a shitty mechanic. Simple tests would tell you if the sensor was faulty, not by paying to replace it.