Fix for me when I had the P0180 code, the fix was a new fuel temperature sensor to the tune of about $125. I went through the diagnostic steps in WIS and the results didn't make sense to me, nor did they solve the problem, so after exhausting my options, I did what I hate to do and threw a new part at it and that fixed it. Been a couple of years now and all is well. I'm not running bio-diesel in mine though.

__________________
Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles