Hi, hope somebody can help!

I have a 2010 1.4 punto evo. Last week the generic warning light and engine management light came on with the message 'start stop unavailable, check engine'. A day later after 3 start ups the lights went out. Fast forward a week and the same lights and message came back on. I've had it hooked up to a diagnostic machine which came up with no faults/codes. So the lights were re-set.
Today the lights and message have come on again. Any ideas?

The car is driving fine, no loss of power, no strange noises. The only thing to mention is that I seem to have used more petrol than usual.

Thanks in advance.