I have a Peugeot 207 automatic (2007). I have the same error message showing up "faulty air pollution" when I start the car & then the warning symbol for the engine stays on (left on the dashboard). I had a diagnostic test done & nothing came up- phew. I think it must just be an over sensitive/ faulty sensor. I have found a way to stop the error message coming up...start the car & then open the left front passenger door & open the bonnet. Turn the engine off & on again & shut the bonnet. Error message disappears. It does come back every couple of weeks but I'm reassured that nothing is actually wrong as this always gets rid of the error message & the diagnostic came back clear. I did have the "check oil level" error message before, but this was because the oil level was low. Topped up the oil level & then error message went & has not come back. Hope this helps!