Hi Jens
If I am not mistaken, I think that a HTTP 200 response (even with a soap fault body) will not trigger the fault response path, and therefore does not go through any configured fault mapping. I will need to double check on this.
If that is the case, if you cannot get the web service provider to change the behaviour, I think you need to handle both normal response and soap fault response in the same response mapping. As the normal response and fault response have different root element, you might (or maybe not?) need a Java mapping to handle the different root element in the same mapping. You can map the soap fault text field to a new ErrorMessage field defined on your sender proxy interface. In this case, the ABAP logic checks the ErrorMessage field in the response structure to determine application errors such as this.
Rgds
Eng Swee