How to know if an "overlap" include another same field ?

You can use the Group Processing option in the AreaOnAreaOverlayer set to the field code. In doing so, it will only compare features with the same code.

It doesn't work, because with this method I have less features than without this method. I don't want only with the same code I want all features with the information in a field if they are the same code or no and nothing is rejected. The result is weird

I see. In that case, I would try using the Generate List option to create a list of the field codes for each overlapping area. You will need to filter after that to determine the areas where all the list attributes. For that, I would look into the ListHistogrammer, ListElementCounter, and TestFilter.

I don't know if it works or no.

To make the list, in transformer "AreaOnAreaOverlayer" options, I filled as you see on the screenshot (click on "expand post"). But in output, it doesn't change anything, I can't see de list. It's normal? After that I used the transformers you told me but with "Listelementcounter" the field "count" is the same that the field "overlap", it seems weird, and with the transformer "ListHistogram" I see anything. I don't know if it's normal. I think I didn't understand you ?

Thank you for your help

The number of overlaps would be the same as the number of list elements. You can then use a ListSearcher to see if the value for CODE_SITE appears in the list.