96 neon trouble codes

I have a 96 neon, the check engine light came on a couple of days ago. The codes are 12, 72 and 55, can any one tell me what these codes are and how to correct the problems.

Thanks:nono:

12 - is battery has been disconnected within the last 50 key-on cyles (nothing to worry about)

72 - is a bad catalytic converter (replace cat)

55 - end of codes