Engine code Reading Software??

[Simpson, James H]

Does anyone have PC based software (windows or dos) for reading engine
codes.  I'm looking for Turbo Pascal, Visual Basic or even Assembler Source
code.  Doesn't have to be fancy.  I just need to read the data stream from
the TX pin on the diag. connector.  My application is early Jeep 4.0 Liter
(Renix system).  I'm grabbing at straws here.

Thanks in advance if you can help.

Jim