Hi keith
On the end of the the crank you put the rear crank seal then i believe there is some crank still petruding to tap the relucter ring on and the crank sensor picks up off this. I will no more when I get the car stripped down. Ive enquired about the relucter ring and it apperently comes pegged up to the seal and only fits in one place. I will take photos when doing job.

Good luck with the pico learning curve.