The following URL, although a VW site, has a good explanation of what
OBD-II is, why it exists, and how it is used.

http://www.bentleypublishers.com/tech/vw/vw.dtc.table.htm

or if you want the official Dodge info, try http://tinyurl.com/a9qcr

Among its information is that PCM stands for Power Control Module. This
is the computer that monitors and controls the Powertrain.

Looking down the list, you will see:

P0602 Control Module Programming Error/Malfunction

This means that there is a problem with the computer. About the only
thing you can do yourself is disconnect a battery lead for 15 min, which
will reset it. If it comes back, you need professional help.
http://www.dodgetalk.com/forums/attachment.php?attachmentid=38075