Saw this mentioned in the FF 3-Door buying guide and wondered what it is and how it works

I know its part of he electronic ignition system

 

It is literally a camshaft position sensor.

 

Ah right cheers

And it will have a rotar arm up the top then?

 

the reason we need a phase sensor and a crank postion sensor is, we all drive four stroke engines, this means that our cranks must rotate twice for every power stroke! and because we want sequential injection (so the injector only fires once per cycle/two crank revs) we need a way of telling the two crank cycles appart,,,, hence the use of a phase sensor