Benz World has your fault codes listed as;
P2311 = Can communication with engine system faulty.
P2312 = 1 or more messages not on Can-Bus or engine temperature not plausible.
Sounds as if the DPF was diagnosed as faulty and causing the limp mode. As the same problem is still there,it seems the problem was elsewhere.
Good luck with it Peter, trust you got paid?
Cheers, Gwyn