My renault megane is chuggy and the error code is DF109?

I have just paid for my renault megane 03 2.0 16v to be put on the diagnostic. They have spent over 2 hours on it and can`t work out what it is........its saying low fuel ??? with error message DF109, they have asked to keep the car for a couple of days so they can check everything ........i can`t afford this so wondered if anyone else had, had this problem ??????