This morning my G37S alarm/panic went off twice. I canceled them and after the second one,I went out, opened and closed the doors, trunk and hood. A little while later I started my car up to let it warm up and let the ice to melt off. A few minutes later when I got back in the car to leave, I noticed the "No Key" warning didn't go out when I sat down. I turned off the car and restarted it a few times and the "No Key" light stayed on. I tried putting the fob it in the socket, with and without the door key in it and that didn't change anything. Also installed a new battery in the remote. Than the car wouldn't start. I could insert the fob and get the "Push Clutch to start" but when I did that, it would say "No Key" when I pushed the start button. I disconnected the battery for a minute and after that no change. Noticed the tiny corner lamps on each corner of the car were lit up with the car off. Disconnected the battery at that point because I was late.

Drove another car to work and when I got home, I reconnected the battery and it started right up! When I started to reprogram the auto window open limits, as soon as the right window got all the way down everything turned off except the engine. No lights or displays working and all lights were inop, but the engine ran so I got it into the garage. When I tried to restart it, I got the "no key" again.

 

I just had this problem two days ago. You have to disconnect the battery and check all the fuses. After you disconnect the battery to and hold the start button for ten seconds to completely drain the power from the ecu. I had a 10 amp fuse that I believe was called ignition blown. It's in in the upper left hand side of the fusebox. I also had a 20 amp fuse blown that was on the lower right hand side. After you check all fuses put the key into the key slot and reconnect the battery and it should be fixed.

 

No fuses blown. Now the windows are down and won't come up after reconnecting the battery.

 

Make sure the doors are closed to see if the windows come up. Maybe that helps.

 

Did you use a multi meter to test all fuses or did you just use a visual check to look at them?
Check for water leaks, anything wet or corrosion around the BCM

 

I took the positive battery terminal off so I could get a better look at the fuses coming off of it. Previously I'd only removed the ground wire. The fuses looked fine and after I reinstalled it everything is back to normal. Not sure if I seated a bad connection or if it was a coincidence. Need less to say I won't be surprised if this comes back again.