Mercedes ML Diesel Battery Draining

That sounds frustrating I had a similar issue with my BMW Same symptoms error messages weak lights discharged battery It turned out to be a faulty IBS Intelligent Battery Sensor on the negative battery terminal It was causing a parasitic drain Have you checked the battery terminals for corrosion or damage Also have you had the battery load tested It could be a combination of a failing battery and a dodgy sensor

That IBS sensor rings a bell I'll check the battery terminals first thing What does 'load tested' involve And was the IBS sensor replacement a DIY job or did you need specialized tools

A load test puts the battery under a simulated heavy load to see if it can maintain voltage Most auto parts stores will do it for free As for the IBS sensor on my car it was a bit fiddly to get to and required disconnecting the battery and some careful maneuvering I ended up having a shop do it They confirmed the IBS was the culprit Honestly with the risk of messing with the car's electronics I'd recommend getting a professional opinion It might save you headaches

I checked everything and it all looked fine I took it to the shop The battery sensor was indeed defective and the repair cost me 315€ It runs great now no more discharged battery Thanks for pointing me in the right direction