[dkmura]

Welcome and sorry to hear your problems. The Nissan Immobilizer (NATS) is pretty effective, which is why Nissans are not stolen as often as Hyundai/Kia are. You need a factory trained technician with a CONSULT III diagnostic tool to reprogram your NATS system. This is not a DIY project and don't waste your time looking for one.

Also, bring your title and ownership documentation to the dealership to show that this is your car. You may as well have them cut two keys and FOBs, so you have a spare. BTW- there was no factory NISMO 350Z built back in '03. You likely have a dealership/aftermarket kit installed.

 

[dkmura]

Since we never heard back from the OP, we don't know what s/he did. Do you have a spare key to use? Even the valet key will help stranded Z owners get into their cars.