I think you will have a problem unless you make contact with someone who is familiar with the same stuff. For anyone else there would be a huge amount to study before they could offer useful advice. They would also need to have the same hardware (including a suitable Nissan). (I haven't had a car for 4 years now).
You say
The consult cable works when used with a Serial-USB adapter and a computer to access the information.
. Is this using some off-the-shelf software or some PC code that you have written?
If you have off-the-shelf PC software I suggest that your first step should be to develop your own PC code before trying to get it to work with the Arduino. Programming on the PC is much easier. When it works it should be reasonably easy to transfer your learning to the Arduino.
Maybe there is a web Forum about doing this stuff on a PC?
...R