flywheel sensor

Hi i have a 1.8 t plate freelander,dose anyone know how many wire are there for the flywheel sensor,i know there's two in the plug but i have found another that looks like a earth that has broke sometime is this ment to be there as the timing is running out and poppin etc under load. thanks

The third wire is a shield to prevent interference.

If its popping and farting, change the sensor. I've replaced a few in my time for this fault.