Fuel pin seized in the injection pump. had it happen on a 200 (same pump) and was as flat as a wet fart!
Item B, 5 mins work to get at, only 4 screws to remove.
Crap old pics, but you can see what I did, pics dated 2015 and all still okay.
Just wired to a toggle switch under the dashboard.
Car runs fine even with the pump switched off, but will lack power on hills until you switch the pump back on.
Also...
Blocked dpf is the end result of something else failing.
All the inactive codes will have a part to play in this.
Ps D4 belongs in the discovery section.