Disengage immobilizer?

Nissan uses a split system like many others, the fob uses one system, but the keys use a different system. The security light on solid means that part of the key recognition system has failed. The most common is the NVIS module on the steering column. Its job is to send out a pulse that triggers the transponder in the key, which sends out a code that the NATS then looks in memory for. If the code matches a valid key code everything works. If not, you can get a no start like you have. Testing it requires a scan tool to read the immobilizer and see if it responds, or you can do what many who don't have that do and just replace the NATS module and see if they can get it to work. To give you an idea of how bad their support can be, the first image is all they list in the remove and replace directions for the module! However, to make it easier you will need to remove the upper and lower covers on the steering column by looking under it and removing the screws, then there are clips that hold the halves together. Once off the NATS module can be replaced. Then you need a scan tool to initialize the replacement NATS.
This is the description of its operation.

NATS (Nissan Anti-Theft System) has the following immobilizer functions:
- Since only NVIS (NATS) ignition keys, whose ID nos. Have been registered into the ECM and IMMU of NVIS (NATS), allow the engine to run, operation of a stolen vehicle without an NVIS (NATS) registered key is prevented by NVIS (NATS).
That is to say, NVIS (NATS) will immobilize the engine if someone tries to start it without the registered key of NVIS (NATS).
- All of the originally supplied ignition key IDs (except for card plate key) have been NVIS (NATS) registered.
If requested by the vehicle owner, a maximum of five key IDs can be registered into the NVIS (NATS) components.
- The security indicator blinks when the ignition switch is in "OFF" or "ACC" position. Therefore, NVIS (NATS) warns outsiders that the vehicle is equipped with the anti-theft system.
- When NVIS (NATS) detects trouble, the security indicator lamp lights up while ignition key is in the "ON" position.
- NVIS (NATS) trouble diagnoses, system initialization and additional registration of other NVIS (NATS) ignition key IDs must be carried out using CONSULT-II hardware and CONSULT-II NVIS (NATS) software. When NVIS (NATS) initialization has been completed, the ID of the inserted ignition key is automatically NVIS (NATS) registered. Then, if necessary, additional registration of other NVIS (NATS) ignition key IDs can be carried out.
Regarding the procedures of NVIS (NATS) initialization and NVIS (NATS) ignition key ID registration, refer to CONSULT-II, IVIS/NVIS.
- When servicing a malfunction of the NVIS (NATS) (indicated by lighting up of Security Indicator Lamp) or registering another NVIS (NATS) ignition key ID no, it is necessary to re-register original key identification. Therefore, be sure to receive ALL KEYS from vehicle owner.
System Composition
The immobilizer function of the NVIS (NATS) consists of the following:
- NVIS (NATS) ignition key
- NVIS (NATS) immobilizer control unit (IMMU) located in the ignition key cylinder - the part that commonly fails.
- Engine control module (ECM)
- Security indicator