Hello All, I am new to the forum and would appreciate some advise on my GLS. I purchased it from a non-MB dealer and all is well except the Eco Start/Stop doesn't work, please I know some of you don't like this feature and to be honest this is my first car with the feature and never experienced it, maybe I will like it and maybe not. The light is green at every start, no messages on the popping up, no CEL, all other functions on the car seems to work as normal, even turned off the AC. After doing some searches on the forum and google I found nothing helpful since the light is green and can be toggle on and off manually. On the day the car was picked up the dealer stated that the battery was dead since the car was sitting for a while in their lot, they boosted the battery and drove for 3 hrs (PA to NY). I use the car daily and the battery seems to hold fine. Could it be the AUX battery? any other recommendations please...thanks.

I'm trying to understand your question. The Eco Start/Stop does not work?

Can be battery is weak or the engine temperature is not high enough. it can also be something else.

the Eco Start/Stop doesn't work, temperature seems normal.

There is about a dozen of potential parameters than need to be met for ECO stop to work.
Battery needs to be fully charged and that takes some driving before it will reach the stage.
You can blindly replace the battery, but you will not go far on those vehicles without a scanner.
Autel dongle sells for $49, so not much excuse to not own 1.