I have a 05 G35x with the automatic, recently my when I slide my shifter over from Drive "D" to the manual mode it doesn't change at all.. just stays in "D" and doesn't show "M1".. it still shifts fine like its in drive and you can push and pull like if you were to be in manual mode yet it doesn't switch over.. wtf? is up with this.. LoL

 

My initial gut-feeling/total educated guess... Something is fubar in the shifter assembly that isn't telling the car you are in manual mode and not D. Could be a mechanical switch that is broken, or an electronic connection that isn't being made. But either way, the car doesn't know you've moved the handle from D to manual mode for some reason