Antipollution gives fault error.

Friends We have 307 1.4 diesel car 2 days ago Antipollution fault error. My father made some things that took the car to the master, I don't know in detail. The cost of this is almost 1300 TL. I have read in some locals but there are those who say very different things. Exactly what should be done. I would be happy if you help

Thanks in advance.

Get well soon, my nurse, first of all, if you examine the link I gave, you will most likely solve your problem.