i have a 2006 g35 coupe. i lost my keys and had a locksmith come make me new ones. they ave been out 3 times with different programming machines. the problem is that it starts the car one time and thats it. after the first time it goes into lock mode. the red light on the dash stays on solid when the key is put to the on position. have tried to get out of lock mode with the 5 sec. on 5 sec. off sequence with no success. why is the bcm not holding the new key code?

 

Could be a failing BCM, could be an incompatible machine the keysmith is using. I would use that one start to drive to Nissan and have them program it or at least diagnose exactly what the problem is.