Although not visible, all 8.4x nodes have a default Domain Connection Password of ‘PS’. During the security hardening process for Peoplesoft 8.5x this type of hidden password was made required and the hidden defaulting logic removed.
To connect to an 8.4x system from PeopleTools 8.53 and 8.54 onwards you must specify the password. You can override the password in the config of the 8.4x system to be something other than PS – in fact you should do that. But to get things working when you cannot “ping” the old node, try ‘PS’ (upper case) as the password.