my buddy ahs a 2000 180 TT quattro
he keeps getting a knock sensor code. I vaged it and sensor 3 and 4 are stuck at .250 v and do not move when revved, driving etc. does this mean they are shot? could it be wiring? how hard are they to change? i think i found them somewhere for about 85-120$ so thats not tooo bad. id imagine they are located in the intake manifld side of the engine? any information is greatly apreciated. i tried the TT forum, got a few views, no help though.

There are only two .. each monitors two cylinders.<ul><li><a href="http://1.8t.org/~quattroman/Audi%20B5%2097-2001/Fuel%20injection%20and%20ignition/AEB/MFI/24-1%20Motornic%20MFI%20&amp;%20Ignition%20system.pdf">Bentley's</a></li></ul>