Nissan Repair: 07 armada no start intermitently, controller area network, nissan vehicles

Question
I have a 07 armada with a nats code 1615 difference of key.I have already replaced the key twice and initialized keys with no problem.Replaced the antenna amp,bcm,ecm and ipdm with no sucsess. Checked for interferences, none.Performed voltage drops for power and ground all good.Added a extra ground to antenna amp,n.g.Still will not crank sometimes and gives the same code every time in engine and nats diagnostics. Checked and replaced battery in vehicle. Sounds to me like it is going into lock mode for some ungodly reason because after you remove the key and reinsert it three times,on the fourth time it will start and it may crank forty times before it acts up again. Any ideas or help telling me what to do next would be greatly appreciated by me and my customer. About to go insane. thank you very much! keith!

Answer
Keith,

Something is stepping on the RF between the key and the vehicle.  A cell phone, aftermarket bluetooth, radio or other aftermarket part.  You could shield the radio and amp with foil or Dynomat.  But, remember that it has to be grounded.  I have seen this in Corvettes since they do not have much metal shielding.  Lining inside the dash, adjacent to the radio would probably help.  Also, if there are heavy duty lines feeding amps and speakers those ought to be shielded too.  You probably do not have an RF meter at your shop.  But, if you did you could dial into what is going on in the vehicle.  Remember that the Armada has a controller area network and changes to the factory wiring will mess with the computer.  Oh, also check with the customer to see if they have other Nissan vehicles and if they have both keys on one ring...