Manual,. .. .I dont have a specific answer to your question, however <a href="http://www.airbus.com/pdfs/customer/fast28/a319.pdf" target="_blank">FAST Airicle on the A319CJ fuel system</a> gives dome more detail on the minibus fuel system operation.. .. .The FUEL PRED page on the MCDU has the FOB calculated from the FF and FQ, if either fails a message "Sensor Invalid" appears.. .. .I think now on the 330 a new ECAM warnin "FUEL FU/FOB DISCREPANCY" and "FUEL LEAK - CONSIDER" appears when the EFOB and FOB differs by 3.5t.. .. .Z