dcaprio

Hello, New Member and first time MB owner. I purchased my 2016 E350 Sport 4Matic back in July 2015. I just started getting the "Auxiliary Battery Malfunction" warning light on the dash. Reading many posts one MBWorld has me a bit confused. Is this warning for a small battery in the dash or the larger battery in the spare tire well in the trunk. I actually have an appointment at the dealer but it is not for a few weeks - earliest they can get me in supposedly. If it is an easy replacement I don't mind doing it myself. I just am not clear on which battery is the culprit. Any ideas? I am assuming it is the trunk battery. Some threads mention a smaller battery that is located in the dash. I didn't want to go into the dash if I don't need to. I have also lost the ECO start/stop function, again leading me to believe it is the trunk mounted battery.

Thanks in advance for any assistance!

davidjohnbamber

Your ECO-Start battery in the trunk needs to be replaced. There are a lot of posts here about ECO equipped cars having the auxiliary battery replaced, after having a Auxiliary Battery Malfunction message on the Command screen. I went over 2 weeks before I had my battery replaced after getting the message on my 2014 E350.

PatrixUSA

This symptom (losing your ECO function) indicates to me it is the trunk battery, as I had a similar issue months back that was corrected by replacing said battery.

+1

nycebo

Same here. Just had this replaced at the dealer under warranty two weeks ago on my 2015 wagon. Its failure resulted in no start stop and no hold when waiting at a light. Swapping for a new battery fixed both immeditately.

Of course, the squeak in the driver's seat persists! :-(

GigRig

I have read your post. And I have had the same problem on my 2014 w212, dealer replaced the auxiliary battery, no more issues.
Now to address that annoying squeak in your driver's seat.
If you check you will see that the seat belt portion that is connected to your seat, rubs against the leather and creates a squeak, It did in my vehicle anyway!
I used a piece of black felt tape that has a sticky back, and attached that to the backside of the seat belt clip. (Female end). No more squeaks!! I hope this works for you.