Hello old thread. I am experiencing a similar problem.
I drive a 2000 156jtd (77kw one) I bought in september
Nothing looked suspicious, but I bought an elm cable and fiatecuscan right away anyway.
Until a week or two ago all was relatively fine...
Relatively meaning every once in a while I got P0220 and the engine heavily drops rpm usually when starting and the problem disappears if I press the gas pedal more than about 2/3.
It did not appear these last two weeks, mentioning just in case anyone thinks it could be related.
Now on a few occasions 2 weeks ago when stopping at a traffic light and engine got to idle rpm it died,
everything normal except the engine stopped spinning and battery/oil lights on as when the engine isn't turned on, no warning lights.
The engine started normally right after. I read it out as P1320. On some 3rd occasion the engine didn't start for some 30sec, luckily I just came home and was parking.
Later the error started appearing while driving as well, in this case the engine cut out and regained rpm right away, felt like a slight jerk.
Over the days the problem escalated form a fraction of a second to upto a whole second and injector warning light came on briefly.
As for today the engine cut off and didn't regain rpm at all. I pulled over, tried to start it unsuccessfully, made few calls and waited some time, after the engine cooled off it started normally.
Drove to the 1st exit where it died again, waited cooldown and started, drove a bit with some jerks then died again. Got it towed.
This time I got P1320 and P0335. Injector light on until next successful start. :S
Any ideas? How did the mentioned cases turn out?