Hi Anant,
Even I'm facing similar problem during an attempt to call PI custom Service as external Service and there is no standard service involved.
In our case, only outbound communication is exist.
1. Created an external service referencing PI custom service URL.
2. Create a custom communication scenario and added above service in custom outbound Services
3. created a new communication scenario in Silverlight and provided PI user credentials which is not exit in C4C.
4. Check Connection and Check Service both are successful. In SOAP UI also this runs correctly and provide response.
5. In our case PI user id is system generated user id not exit in C4C. So how required authorization can be give ? Please respond as soon as possible.
Getting following error message : SoapFaultCode:5 Server Error
<GetPricePIServiceMT_SOPricingResponse xmlns:prx="urn:sap.com:proxy:L3Y:/1SAI/TAS995BE70EF85C120797CA:804">
<MT_SOPricingResponse/>
<CommunicationFault>
<MaximumLogItemSeverityCode>3</MaximumLogItemSeverityCode>
<Item>
<SeverityCode>3</SeverityCode>
<Note>SoapFaultCode:5 Server Error</Note>
</Item>
</CommunicationFault>
</GetPricePIServiceMT_SOPricingResponse>
Thanks
Shridhar