Just a potential FIX for you bashing your head against this particular wall,
The problem, a 2008 is220d, 110k miles, with embarrassing quantities of white smoke from exhaust that smells of diesel fuel.
My parents car has been smoking like a pig for the last few months,
Diagnosis....
Garage condemmed the DPF and replaced it..................Still smokes.
Garage says "just keep driving it, the smoke will soon stop"............It didn't
Garage says "er, drive it some more"...................Still smokes.
Garage yanks the injectors and send them off to be tested, by people who are not idiots..................non idiots send them back with the verdict, injectors are perfect...........................Still smokes.
Garage now say they are sure it is the turbo which will need replacing...................At which point I get involved and rescue the car.
No sign of misfire, compressions good, no play on the supposedly fragged turbo, no headgasket doom.
Not trusting the fifth injector, I unclipped the fuel line and plugged it by clipping another injector on it.
Went for a drive, white smoke gone! So confirming fifth injector misbehaviour.
Changed the fifth injector, a total git of a job............Smokes, Argh!
So it is the ECU telling the fifth injector to keep on squirting.
Techstream turns up from ebay, so plug it in.
The dpf pressure values are all over the shop, so tee in a magnehelic guage, which disagrees with the values from the software.
Wiggle wiring, AHA! Gotcha! Pressure values in the software change in sympathy.
So I remade the wiring from dpf sensor to the ECU and then got good values for the dpf sensor pressure.
The ECU "learns" whilst you drive, but the corrupt dpf pressure data had totally confused it. Unplug car battery for ten minutes, reconnect, ECU starts to relearn with good data. Relearn the window winders by driving them for a couple of seconds against their stops at each door switch.
AND THE SMOKE STOPPED! and mpg has gone up from 25mpg imp to 40+mpg imp.
The magnehelic gauge reads 5kPa (20 inches water gauge) when regeneration of the DPF now starts.
So to recap, check the DPF pressure sensor to ECU wiring carefully before spending lots of money on the garage partswap goosechase.
Good luck on what is a fantastic car.
Warning!!!!!!!!!!!!
! I only disconnected the fith injector for long enough for diagnosis, if it is disabled for too long, the DPF will probably clog up! I only disconnected it for 20 miles.