Your post was a while ago .... I have the same model (with 64,000 miles on the clock and 4 years old) and have had the same issue for a few months. Intermittent "depollution system failed" errors. The car has been to two different dealers - the first said it was the glo plugs and replaced them at great expense but the problem came back ..... the second dealer say its "over pressure issues on the turbo" and the turbo itself needs replacing at a cost of over 1000 pounds - I have asked them to escalate this to citroen as that seems a bit steep for the cars mileage. We will wait and see .....
