The "anti-pollution fault" is the generic message given by some models of Peugeot vehicles, most notably the Peugeot 307, regarding engine management faults relating to the vehicle's emissions. It is set off by errors in the vehicle's anti-pollution systems, including errors in the pollution filters, problems with the MAF sensor or faulty EGR valves.
The anti-pollution fault is usually a warning to have the Peugeot's emissions checked. It is more common in the Peugeot 307 as well as any Peugeot vehicle that is made to run on diesel. In diesel vehicles, the anti-pollution fault is usually accompanied by the unblock diesel filter message.