error code p1140

I have a code p1140 and this is after replacing the crank angle sensor (recalled on 2000 sentra's). In fact I am on my third one. The code has been cleared manually after different efforts to stop the error from re-appearing.

My question?, are there two of these sensors I need to worry about? I haven't been able to see one of these sensors on the battery side of the engine. Or do I need to look at some problem entirely different?