istop not coming in and fuel consumption

[singingsnapper]

For the last few months, my car's (2015 Sport Nav auto 175) istop function hasn't been working.  Also I've noticed that my fuel economy has taken a nose dive.  I was initially getting an indicated 42mpg on long runs, but am struggling to get 37 now.  After a run to London and back, it's just below 36mpg.  I've put 9k on it since purchase in July, and will probably put it in for a service soon. 

[BigAl]

If you have the istop app on when driving, you’ll be able to tell what is preventing it from working. There three indicators are engine, a/c and battery. On mine the battery indicator kept going off when the engine was idling, preventing it from working. After a LOT of testing, they came to the conclusion that there was a failed cell in the battery and Mazda authorised a replacement.

Alan