Hi all,
I have a 2014 c350 with the blue efficiency v6 engine.
A while,back the "ECO" mode where the engine switches off when the car is stationary stopped working so I took it, back to the dealer to check it out.
They determined that the battery was faulty and supposedly replaced it.

3 months later, the problem has started recurring.
I noticed that it took longer for the "ECO" mode light on the dash to turn green, then that the engine would stop for shorter periods, (under a minute), before restarting.
Lately it has got worse with the "ECO" light never turning green at all during most short duration trips of under 20 minutes or so, but randomly appear to work normally after the car has been parked and restarted after a short time.

I have it booked to go back to the dealer later this week, but would like to know if anyone has any ideas what could be going wrong as I want to make sure they test and fix it properly this time while it still is covered by warranty.



Thanks in advance for any suggestions.