hi driving my C220 cdi W204 I noticed an issue with the eco mode when I started the car the eco symbol was yellow as normal but during the journey I looked at the speedo and noticed the symbol was missing I hadn't switched it off, the button was off as well I tried turning the button on but nothing was happening it stayed off the whole journey albeit a short 5 mile journey but when I reached my destination I keyed off and on and the symbol reappeared on the dash when I restarted the car later on the system behaved as normal eco symbol yellow then turned green after a couple of minutes, is this a sign something is on the way out like the battery or I read somewhere the system will disable itself if the timing chain is out .