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i have a C250, W204, 2011 model, and i noticed that the ECO mode is not working anymore. When i turn the car on, the ECO button light is green and the ECO sign appears in the cluster. After 1-2 min, the ECO sign dissapears from the cluster and the green light on the ECO button goes off. Even if you press the button nothing happens. Previously, you could press the button to enable ECO mode and the ECO sign appears in cluster. The sign in cluster was yellow if car could not meet criteria of ECO mode or Green if it was. Now, the button is dead. No Eco sign appears in cluster anymore. All criterias of Eco mode are met(a/c is off, engine temperature is OK,etc)

Any suggestions please?

Thanks Yiannis

  • Have you had the car scanned for codes? Some codes do not appear as a CEL, but store in memory anyway. My understanding is that ECO mode does the start/stop with the engine. I'm wondering if one of the sensors involved with this is not functioning properly. Maybe one of your O2 sensors is getting lazy ... very interesting. – Pᴀᴜʟsᴛᴇʀ2 Oct 19 '14 at 15:02
  • Hi Paulster2, thanks for the response. I run the car diagnostic from the cluster and no error or message appears and i am planning to take it to Mercedes to have it also checked.I am looking to find if this is happening to others or if anyone knows what is the issue so that i don't have to leave the car to Mercedes running all type of diagnostics and charging me.The strange thing here is the Eco mode is working and button as well only the first 2 min. After not sign in cluster and button does nothing... – Yiannis Oct 19 '14 at 15:23
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    I'm just trying to help you dig. I don't know much about MB, but seeing as how it goes from being on to shutting off in two minutes, seems to me there might be an issue with one or more of the sensors having to do with fuel mapping. A lot cars go from a open loop mode to a closed loop mode (normal operation) in about two minutes. If your car is not going to closed loop, this could be shutting down the ECO mode. If one of these sensors is bad or is out of tolerance for the ECO mode, it could be your issue. – Pᴀᴜʟsᴛᴇʀ2 Oct 19 '14 at 15:40
  • Thanks for the comments. I take them on board and will investigate further to see if these can be the reason. – Yiannis Oct 19 '14 at 21:58
  • @Pᴀᴜʟsᴛᴇʀ2 do you want to submit that as an answer? This question seems specific and targeted enough not to close as too broad or unclear, but more or less a toss up until we can lasso a modern MB expert into our ranks. – MooseLucifer Aug 9 '16 at 19:03
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it is the battery - the primary one. Please do check in the manual that states only fully charged battery will be able to support ECO function to work. When you press down the brake, the engine will stop and other functions (such as air cond, headlights, etc) will be running on battery and hence your battery needs to be good for the functions. p/s - the battery has to be of same capability/power or more not just any other battery. thanks

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I've had this exact issue before on the same car and it turned out to be the battery not holding optimum voltage.

Reading the manual and from personal experience, the following conditions need to be met.

  • Battery voltage above 13v
  • Engine at operating temperature (85-95c)
  • Transmission temperature and pressure (There is a small electric pump which runs during stop start)
  • Brake sensor, get someone to check that with the car in drive and the brake peddle pressed until hold appears that the brake lights are lit, it might be brake position or sensor related.
  • seatbelt on? the stop/start system will not engage if you're not wearing your seatbelt.
  • Indicators on? My c250 wouldn't stop/start when the turn signal was on. I believe this was to allow a rapid get away at junctions.
  • Mine would still go into stop/start even with the a/c on if the temperature was close to the target temp set.

The stop/start system is very complex and includes electric pumps and sensors designed to stop the engine in the perfect place to allow a rapid restart. The pumps continue to pump trans oil or maintain system pressure.

If a battery swap and a long drive doesn't resolve the issue, you'll need Merc to plug the car in or you risk replacing good parts or wasting time.

Remember that stop/start

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I agree. My 13 c300 4matic was not working for some time. My brake "hold" mode didnt work either. Finally this AM the FB signal on my car told.me battery was low. I just got started on what was a very weak start. After installation of a new Champion AGM battery, both started working almost immediately. Now works all the time I almost forgot this was an option I did.not want dealer amd 500$ later. Done for $210.00 Hope this helps.

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