check it 1st, perhaps a wire has gone loose or the plug came off.. but for the knock sensor to go there are other problems.. is ur car tuned propperly dude?
DONT drive it with the knock sensor fucked.. its not a good idea..
I had the same problem with my gt a while back. The car used to go into limp mode and the engine warning light would come on.
Like hybrid said, check the wiring etc. My k-s wire got trapped between something in the engine bay and snapped.