2.3 multijet
The light on dash to show a fault comes on then somtimes when driving it goes of,also when you move the wires at the control box in rear it can show fault could it be a loose connection or a sensor how can you tell what the fault is

Buy an obd code reader.

If you have an android phone you can use this one:
http://www.ebay.co.uk/itm/NEW-Andro...stic-Scanner-ELM327-OBD2-vgate-/371247898389?
and the demo of alfa obd
https://play.google.com/store/apps/details?id=com.AlfaOBD.AlfaOBDDemo&hl=en

Alternatively if you have a laptop you can use:
http://www.ebay.co.uk/itm/USB-Cable...506?pt=LH_DefaultDomain_3&hash=item1e9b24c2ba
and the demo of multiecu scan:
http://www.multiecuscan.net/

Sounds like a bad connection somewhere.

Mine are disconnected due to fitting a Hope T-Bar (which made them think I was constantly about to hit a wall!) so I too have a yellow warning triangle on permanently which is easily solved by sticking black tape over it

I believe there's a block connector under O/s/r corner, I would start there as its in the open and gets tyre spray to deal with too