I have a 2012 ML350, scanner has a bunch of codes that leads towards the fuel pump. I have the back seats out, carpet up and do not see any access hatch to get to the pump. Any ideas?? Fuse also blows immediately as i replace it even when the truck is completely off. Had water accumulate in the spare tire well, not sure how but noticed the carpet was damp when I lifted it up. If I jump the fuse the pump or something in the tank sounds like it knocks but wont turn over.

 

I also have a 2012 ML350 with a fuel pressure fault code. I understood the access ports for fuel filter and fuel pump were under the rear seats. (Fuel filter on driver side and fuel pump on passenger side.) I am slowly figuring out how to remove the rear seat back. Hope to get in there tonight. Will be pissed if there are no access ports like I've seen in a couple of videos.

Did you make any progress on your repair?

 

I'm afraid you're gonna have to remove the fuel tank. Here's the procedure from WIS.

 

Thank you so much. You confirmed what I discovered the hard way last evening. I completely removed the rear seats and door pillar trim to be able to pull the carpet back to expose the area beneath the seats. I discovered no access ports for the fuel filter and fuel pump as I had seen in multiple videos of earlier ML fuel pump replacement procedures. In my clumsy attempt to remove the rear seats, I had also already removed everything in the trunk area (floor over spare tire storage area, spare tire and tire changing parts, and all trim surrounding the spare tire storage area). I found no port there either so I concluded the tank must be dropped for this repair on a W166 and I put everything back together.

Edited to add this pic of the area under the rear seats: