whats wrong with my 03 pt man trans on 2003 Chrysler PT Cruiser

when i put it into gear it seems to be slipping all fluid is full and good color. when i let the pedal out in first it just like idles and doesnt even stall out like my clutch isnt engaging. its like this through all the gears.autozone says i need a knock sensor replaced

Asked by for the 2003 Chrysler PT Cruiser