I replaced the battery on my keyfob for my 2006 G35.
I have tried this several times and get the same end result.

Step 2 -The hazard warning lamp will then flash. The lights do not flash therefore it doesn't work for me.

1. Close all doors and lock all doors

2. Insert and remove the key from the ignition key cylinder more than six times within 10 seconds.
(The hazard warning lamp will then flash.)
NOTE:
Key should be withdrawn from ignition key cylinder completely each time.

NOTE:
Do not rush the insertion/removal key cycling process. The side
marker/tail/license lamps and interior illumination will flash twice when this step is
accurately completed.

3. Insert key on ignition key cylinder and turn ignition key switch to "AAC" position
At this time, the new ID code is entered and original (previous) ID codes are erase.

4. Press any button on the new remote controller once. (The hazard warning lamp will then flash)

NOTE:
Do not press the button more than one time in the above step. If the button
is pressed more than one time, the programming procedure will not be successful.
The side marker/tail/license lamps and interior illumination will flash twice when this
step is accurately completed and programming is successful.

If there is only one remote controller skip step 5.

5. Additional ID code entry
Release the door lock, then lock again with door lock/unlock switch
(In power window main switch)

6. Remove key from ignition

7. Unlock driver side door, open driver side door and then close the door. (END)

NOTE:
If you need to activate more than two additional new remote controllers, repeat
the procedure on step 5 "Additional ID code entry" for each new remote controller.