Failure in Citroen C3: Insufficient oil pressure

Friends
someone can do me the favor of helping me with the following:

I have a Citroen C3 1.4 Turbed Diesel, and the 6 months began not to work the turbo and after waiting much to wait for the concessionaire replacement the piece of the catalyst according to the report and function well.
After 10 months the engine began to be separated (off) as a rise while driving through the city, showing the message: insufficient oil pressure and defective antipolucion system. He took it to the concessionaire and reported that they found no failure.

Finally, after so much to be patient, now in January 2011, it took it to the concessionaire because it began to go out more often; After 3 weeks of reviews, passing the scanner and consulting France, they told me that they could not find the fault, and that the French told him that when the engine that the information was recorded in the scanner. As they were not lucky to find the fault, I had to be happy to pick up the car without a complete repair.

Please ... can anyone help me solve this ..?

Thank you ...

Fredu,
Guatemala City