We have owned a BMW 318i from new in 2010 and have covered just 15,000 miles in six years. We have experienced NOX and cam shaft sensor failure twice in the time that we have owned it - once in 2014 and again in 2016 - replacement has cost £750 on each occasion. We bought new, partly to avoid the likelihood of unexpected and unwelcome repair costs. BMW are not very helpful siting 'low mileage and short journeys' as the cause although no one in the sales department warned us of a potential problem at the time of purchase though. Is this problem exclusive to this make/model and what kind of usage pattern (length of journey and annual mileage) would be required to avoid sensor failure?