When driving my 2005 Chrysler 300c it goes only 40mph. Need to know the cause. on 2005 Chrysler 300

I was driving on the exspressway and the my car started to slow down and would only go 40mph. I can still drive, everthing seems okay, it just wouldn't go over 40mph.

Asked by for the 2005 Chrysler 300
scan for codes and live data on post results. could be plugged exh low fuel pressure.