anti pollution fault on my peugeot 307sw 1.6 hdi?

can anyone help me my peugeot 307sw is working itself when the fuel gauge reaches a quater full the anti-pollution light comes on and then the car seems to lose power i,ve filled the tank up and let it run down to the quater mark again and still the same fault,i thought this might of cured it but obviously it didnt can anybody help.