Hi Techie,
Check this sap note.
1930823 - 400 ICM_HTTP_CONNECTION_FAILED 404 Resource not found Partner not reached
Cause
Parameter icm/conn_timeout is used to set the timeout when setting up the connection.
If the timeout is exceeded, an error page is generally displayed with the information
"404 Resource not found" "Partner not reached".
Resolution
Please increase the Instance Profile parameter icm/conn_timeout to "10000"(msec)
on application system and PI system. Please also increase it on the Web Dispatcher, if you use one.If the problem persists, you can increase the parameter to 15000 and 20000.
Regards,
Praveen.