It's not so much a TDDi/TDCi thing.
The problem is that any Ford van of either denomination, pre-2004/5 ish, is not OBD compatible, so most aftermarket code readers, apart from the official Ford IDS, may struggle to give an accurate reading of the codes.
I never had the use of my ELM327 with Forscan when I owned my Mk6, mainly because I never needed it, so I can't really give an opinion of how well it works on an older van, but to be fair, for the price of the unit at around £20 and a free download of Forscan, it's well worth trying it out, assuming that you have a Windows enabled laptop already
The necessary plug that you need is at the base of the steering column, usually under a cover.