Citroen c5 2.0 ltr hdi 2005 model

[Gee g]

Hi can anyone help I've just fitted a new clutch and flywheel to my c5 now engine management light has come on along with de pollution system fault car has 90 k on clock and had no lights on dash before I took it apart been told dpi fluid could be low is there any way of checking this. Any advise would be appreciated thanks