Engine Management - Lambda Sensor

Recently purchased a 2005 StreetKA - drove about 100 miles before engine management light lit up. Friendly off duty mechanic told me it could only be the lambda sensor of the air mass meter. Was going to do the lambda sensor myself but could not shift it no matter what I tried. Took it to Top Tread Tyres in Sheffield for a service and asked them to give it a check - they cleaned the air mass meter and the fault cleared but came back on after only a few miles (during their test drive) so they removed and replaced the manifold lambda sensor (at a very competitive price). This seems to have rectified the problem but be aware the engine management will lite up for all manor of reasons and getting it tested can be costly - cheap engine diagnostic tools are widely available to purchase so you can do your own checks. Apparently Ford cars on board computers run a diagnostic check every 100 miles.