NW-BPM Synchronous Activity - Exception handling

Hi,

I'm having an issue with the exception handling in case of synchronous activity. The activity is an interface to a non-SAP system and returns back a response/fault message.

Now in case if the processing is success, it works fine. However in case it is not, there is an error in processing or the execution was not successful in legacy system the BPM Process errors out but the incoming response message is successful or in delivered status.

What I found in the log is "Fault processing: No exception class found for faultName "

I was wondering if you can suggest me what should be done here in SAP NW BPM Process to handle this kind of behavior. Do I change anything in SAP-PI side?

Thanks in advance,

Arnab