Late last year the fuel economy of our 2005 Citroen C4 2.0-litre petrol started increased from its usual mid-9s to high 10s. A warning light then came on indicating a problem, which was diagnosed as ...

Problems don't fix themselves, you had a problem and I'm guessing you still have it after replacing the faulty sensor. I would have the car checked again in an effort to trace the cause of the problem ...