It can still work however if its knocked a couple of teeth off the cogs inside the box it might not be opening fully, thus registering the fault.
Best bet is to take the box off and inspect it inside, or just shove a new one on.
http://www.fordpartsuk.com/shop/focus_st170_inlet_manifold_runner_control_imrc_813 .htm
Certainly not cheap, but its either that or a fault inside the inlet manifold itself (unlikely but not unheard of) which is going to be lots and lots of money to put right.
Could try the price from ford from the box. If I can find the invoice for mine I'll let you know how much ford charged me for mine when I had to replace it.
Rich
