I have a problem with my misses C4 and it is above my technical knowledge to diagnose the problem. It's easy to fix my Xantia (all you need is a hammer

The issue with the car is that "Engine fault, repair needed" alarm has occurred. I have a Lexia and erased the faults but and its good for a day or two then it reapers. The car otherwise drives ok, just sometimes it looses a bit of power. About a half a year ago the car went into "Limp mode" with a total loss of power and I erased the faults and it never reoccurred.
This picture is from back then when it went to limp mode:

And this picture is from now:

If someone can point me into the direction of investigation or which part needs to be changed I would really appreciate.
Thank you!