06 peugeot 407 estste?

You COULD have done aGogle search.

Some stuff I found (plus some dedicated Pug forums, which may be of more help)

http://www.honestjohn.co.uk/forum/post/?t=91263

http://www.peugeotforums.com/forums/maintenance-9/peugeot-407-depollution-system-faulty-347/ (Especially last post)

http://www.peugeotcentral.co.uk/ftopic-9185.html

HTH
March 2017