So I recently bought a 2013 E350 Bluetech Diesel Sedan. I’m loving it.. I mean at least to look at since I’ve been in quarantine since I bought it. I was trying to find out why the automatic trunk wasn’t opening and closing. I guess it need to be reprogrammed or reset by the dealership?… that’s not why I’m here… I lifted the trunk floor mat and found this beautiful thing next to my DEF tank unplugged. I’ve googled searched to figure out what it is and why it would be unplugged but my ADHD wouldn’t me. patients isn’t my thing. Anyways car runs fine without it plugged in… a few codes about the doors, seats and the trunk nothing to exciting…. And because I’m an idiot I plugged the bad boy in to see what it did if anything…. Took it for a drive and a few other codes came up. More so about the DEF Heater and let me tell you the stench this car was giving off…. It wasn’t pleasant and then we though something was on fire… but nothing was… I made sure everything worked it, and the only thing found was the sunroof wouldn’t close but I feel that’s something different… like it opened fine.. then when I’d close it it wouldn’t close all the way… eventually I was able to get it closed with a light tug… maybe it’s dirty? Anyways … what is this, why would it be unplugged and is it important?

Thank you!!!!

 

W212 diesel engine control unit (ecu)

 

This is DEF control unit.
From your description sounds like you had DEF and probably DPF delete and that is why it was unplug.
By plugging it back, you confused scrambled ECU and that is why new codes come on.
Deleting DEF is illegal all around the World, although some owners don't worry about it.
Check with PO who did delete as at some time you might have to reverse the process.

 

not gunna lie here… I have no idea what PO means

 

Previous owner.