Hi all, new proud owner of a 2004 G35 sedan 6 speed manual with 79k original miles that I got for very cheap that is in pristine condition except for some minor rust along the right rear wheel well and other minor cosmetic imperfections. Anyway, it only came with one key. I have two FOBS that I bought for $15 from eBay that work great but I still only have 1 key to start the car. It's enough for me, but what happens if it somehow either gets lost or the transponder stops working? Can the Infinity dealer get me a new key without having to replace other crazy parts like the ECU and other BS and such that often happens on other manufacturer's cars if you loose the last key? Infiniti Stealership wants $400 CDN for a original key cut and programmed, I can get a aftermarket Nissan key for $15 that supposedly works on certain Infinitis as well (transponder 46 chip) and have a local Nissan dealer cut and program it for $150 as they have the same equipment. But there is no guarantee the aftermarket key will work or more importantly no guarantee the Nissan dealership will do the job correctly and just blame the aftermarket key when things go wrong...
BTW my local locksmiths are absolute crooks, they want 20-30% more than a dealer wants for the same cutting and programming service...

 

Here's how the system works, inside your key in a little slot in the plastic housing is an RFID (Radio Frequency ID) chip.

When you put your key in the ignition there is an antenna right next to the lock cylinder that reads the RFID chip, the data is sent into the BCM (body control module, driver footwell) and if the key info matches what's been programmed into the BCM then the BCM sends the NATS/IVIS (Nissan Anti Theft / Infiniti Vehicle Immobilizing System) unlock code to the ECM (Electronic Control Module, passenger footwell).

When you turn the ignition to START the ECM will send signal to start cranking the engine (starter relay/fuel pump relay) and if it has the NATS/IVIS unlock then it will actually start the engine (adds fuel and spark). Without the NATS/IVIS unlock code the engine will turn over but the ECM will not deliver spark or fuel and the NATS indicator light (security LED light) on the left side of the dash will be SOLID RED while cranking.

If you have 5 sequential start attempts without NATS/IVIS unlock then the ECM will disable engine cranking and the fuel pump and it won't even turn over. You can unlock the ECM by inserting a correctly programmed key.

The key information is programmed to the BCM, you don't have a locksmith or the dealership "program the key", they are actually programming the BCM to accept the unique RFID signal from the key, all keys need to be programmed at the same time, you can't just add one later. Programming mode in the BCM first wipes all key data, then you add all the keys back to it's register. Programming can be done by using the Nissan Consult-II/III dealership tool, or by another 3rd party software designed to work with Nissan. A solid option is Nissan Datascan 2/3. Your V35 platform G35 from 2003-2006 will use NDS 2 or Consult 2, the later version is for the newer V36 platform from 2007+

Other security measures for the vehicle include a security programming match (NATS/IVIS) between the BCM and ECM. You cannot simply replace one of those components without getting the ECM programmed to accept the new BCM, this again requires the dealership tool or 3rd party software. This also requires a BCM decoder key which uses a number off the BCM then decoded via Consult or a web-based decoder, then the pin number you get back is added to the ECM during initial setup.

It's basically two computers that need to be programmed to work with one another, this prevents theft since a stolen BCM or ECM is essentially "unusable" without expensive software to program it.

 

Fobs are handled completely separate from the key, the fob signal is handled by the BCM but it requires a registered key to enter fob programming and you can program the BCM to accept new fobs by using a "pedal dance" sort of method. There are instructions on the internet. The fob cannot start the car so it doesn't interact with NATS/IVIS.

This will not in ANY way affect the registered keys programmed into the BCM.