Can I remove the wiring harness and put dielectric grease in it to protect from moisture?
Try it, it aint gonna hurt anything. The connector is on the trans housing, passenger side, pointing upwards towards the bottom of the floor. Be patient to figure out the connnector, it is a pain. When you figure out the snap release connection, it will easily come off.
If worse comes to worse, see my topic on replacing the valve body to get rid of that code. I hope you dont have to go there.
http://thenissanpath.com/viewtopic.php?t=4910
The Valve body retails for $990. Add 8 bottles of fluid @ $10.82 each and the trans pan gasket for $25.47... Those are the parts alone. I did the job myself and it wasnt too bad, but I am not scared of a little transmission work.