I have a 2 node RAC but failed to create EM dbcontrol. Error "Password for SYS user: Invalid username/password"

I have a 2 node RAC and used the following command to create the EM dbcontrol : emca -config dbcontrol db -cluster STARTED EMCA at 10-may-2008 17:33:42 EM Configuration Assistant, Version 10.2.0.2.0 Production Copyright (c) 2003, 2005, Oracle. All rights reserved. Enter the following information: Database unique name: abcdb