You said that the car has low miles driven by your father. A lot of times, older people drive a lot slower than the average motorist. This can lead to carbon buildup in the EGR system. In my experience with a variety of cars, if the EGR valve is carbon clogged, the internal passageways are also clogged to some degree. The best way I know to get them unclogged is to remove the intake manifold and clean it thoroughly.
As previously stated, this is just discussion until you know for sure what code(*) it is showing.