Well you have to narrow the problem down to which key cylinders are possibly bad. eg: the Ignition, trunk, or door cylinders.
Look in the service manual pag EL-336:
http://www.nicoclub.com/FSM/Q4...l.pdf
Yes thats a 1996 Q45 FSM despite the fact you have a 1994, But the 1996 Q45 FSM is far better when it comes to wiring diagrams and better info.
Yes you can use the key to unlock and lock the car.
But narrow the problem down then visit the Infiniti dealer and ONLY speak with the Senior Infiniti Tech and ask how long he has been there and worked on Q45's.