I have a 300zx, i've heard that you can buy a code reader which is called consult or conzult, and all you have to do is get the software for free and you can download from some website, but where can i get the custom diagnostic connectors

these are the things you can do with this software:

- Checking and deleting error codes
- Manuallly operate solenoids and relays
- Realtime status sensors
- Record, analized and reply the sensor data
- Access to the ECU's Read Only Memory (ROM), Fuelmaps, Timingmaps,etc.
- Temporarily adjustment to tune out car

so where can you download this free software, here is the link:
http://www.300zx-twinturbo.com/conzult/