Your problem is most likely the ECM relay on the ipdm board. The relay is found HERE.
You can test it, replace it, you can test all of them. Have Service Manual Chapter PG, Power/Ground, on hand for the details.
Or just replace the entire board as suggested earlier. That on/off sequence with the key sounds like a relay problem. Cam/Crank sensor issues usually cause some other drivability problems, and you have none.
If you haven't changed the cam sensors, it would be wise to do so. Use the same brand as the new crank sensor.
Don't waste your money on oem or Hitachi sensors. You had a no start, you changed the sensor and still have a no start. It's not that sensor, but be certain they are all fully installed and the connectors are latched.
The Hitachi/Nissan sensors are all hype. They actually suck so bad no other car manufacturer uses them, that I am aware of. Nissan uses Hitachi because both companies used to be, and may still be, in the same corporate structure. They certainly aren't using them for their high quality, as they have an alarming failure rate.
A lot of folks on these Nissan sites needlessly get their panties in a bunch over Hitachi and NGK products.
