And thats another problem with the world. Its getting over complex.The problem is modern cars know the egr has been disabled or blanked and then alter there running putting the vehicle into a less efficient MO and in fact are less efficient and use more fuel because of it !
in fact some now disable the egr under certain conditions to save creating more soot thus trying to save the dpf, it is soooo complex that it confuses itself sometimes and fault codes now are so complex there maybe many versions of the same 'old' code ie sub codes to the main ones.