Interseting! You could be right about the eco mode light relating to battery charge. I have a Subaru Forester that has the ABS light come on when the battery is weak, it is currently on constantly at the moment cos the battery had been flattened and will now not take a full charge. It's not a big problem though co there is still plenty power in the battery to start and run the vehicle. By the way, a new battery would set me back over £80, so I'm happy to keep going with it fr now and just put up with the ABS light being on all the time. But of course, I will never be aware of an ABS fault if one did occur!