The P/N switch is found on automatic transmission equipped cars only and serves multiple purposes.
-power wire for starter is run through it, closed circuit (on) in park and neutral only
-provide a park/neutral status to the ECM so that it can use special parameters for idle and rev limiter
-trunk release safety switch, will only pop if car is in park (?)
-reverse lights
This switch has some adjustability so if for some reason your reverse lights don't come on in reverse but do slightly to one side of it or the other you might check into this.
-power wire for starter is run through it, closed circuit (on) in park and neutral only
-provide a park/neutral status to the ECM so that it can use special parameters for idle and rev limiter
-trunk release safety switch, will only pop if car is in park (?)
-reverse lights
This switch has some adjustability so if for some reason your reverse lights don't come on in reverse but do slightly to one side of it or the other you might check into this.