In some cases the datapump utility gets corrupted .  To overcome it , we need to reload the expdp and impdp datapump utility in oracle. 

 Applicable from 11g onwards. 

STEPS:

1.  start the database in upgrade mode:

SQL> startup upgrade
ORACLE instance started.

Total System Global Area 1.4529E+10 bytes
Fixed Size                  7649368 bytes
Variable Size            8556382120 bytes
Database Buffers         5872025600 bytes
Redo Buffers               93011968 bytes
Database mounted.
Database opened.

2. Run catproc.sql and ultrp.sql script.

@$ORACLE_HOME/rdbms/admin/catproc.sql

@$ORACLE_HOME/rdbms/admin/utlrp.sql