the switch is up near the gearstick.
You can either take the centre console out and look at the back of the gear selector or look from underneath.
From underneath you need to look towards the back of the gearbox. Right at the top there will be a switch poking out of the back, on the left of the gear selctor housing as you look from beneath.
This is a picture from above, when mine was missing:
In the centre of the picture there is a t shaped piece and you can see where it should exit at the rear.
Hope that helps!