Hi all just wondering if you can help me out bought 58 reg Mazda2 1.4 diesel for my son once you get to40 miles an hour it goes in to limp mode put on computer and it says mass air flow sensor put new one but still the same been on all day but can't seem to get it to work any help much appreciated
With this annoying problem

 

When you say "put on a computer " do you mean you have one or was it done at a garage? The reason I ask is was the fault cleared via the computer after you put the new part on if it was not then I could be you will have to do a number of drive cycles before the fault light stays out.