My ML250 has been laid up since the start of the pandemic whereby I had just serviced it. It had also just had a new battery installed, walked out to it one morning and completely dead, changing the battery was a bit of a task with no power. Anyway, the EML light came on not long after and the codes thrown up were;
P0685-The output for Relay Circuit 87 has an electrical fault on an open circuit
P20BD1B - The output for heating element of the adblue tank has an electrical fault on an open circuit.
I can manage the mechanical recommissioning, brakes, servicing, new batteries, auxiliary included but have no idea what Circuit 87 and feel like i'm likely going to need a new adblue heater, I have seen the XeModeX replacement which is more attractive price wise than the Bosch unit from MB.
I suspect something took a surge when I connected the battery in 2020, the replacement battery is also dead, any suggestions as to how to approach the electrical issues, any help would be much appreciated.

In which market/country are you located? In the US owners can receive emissions system modification which made address some of the vehicle issues at no cost to you. When the vehicle is getting the emissions work done the dealer can advise you on your options for the other work needed. You might have to tow the vehicle to the dealer for the above to be successful.

2012 registered ML250 affectionately known as Sherman, US built and feels the size of a tank on UK roads

Nice looking ML! Does the UK have a settlement program for compensation to owners for emissions-related repairs? "Dieselgate UK"?

Not that I'm aware of, it is 9 years old so any UK dealer would most likely decline any warranty claims whether emissions related or not

I got that information from the Daimler webpage
https://www.daimler.com/innovation/d...ecall-faq.html

Perhaps worth some reading and few phone calls? Good luck

Thanks for the information, definitely worth seeing what the dealer says. I think I've got to the bottom of the fault codes, one is an open circuit on a relay in the PCM and the other is related to heater B, which is the element in the Adblue tank. I'm toying with the idea of getting the ML MOT'd and go looking for a W123 230CE as a replacement.