So I have a 03 G35 sedan. When I turn the car off all of the windows go down as if I was holding down the unlock on the remote or I have the key turned to the right in the door lock. I took care of the remotes so I know that they arent a problem. When I put the key in the door and turn it to the left a clicking sound comes from the BCM. Also the only door that locks when using the key is the driver door mechanically, none of the other locks engage/disengage. The alarm also seems to be constantly armed even when I unlock the door so I took the horn fuse out so I would not drive my neighbors nuts. In order for me to keep the windows up I have to have the key in the ON position, roll the windows up, and then pull the neg battery cable.

To me it seems that the car thinks I have a key in the door and turned all the time. Once the car is in the ON position all windows and locks work fine from the interior buttons.

Any help would be greatly appreciated.

Thanks

 

Your description more or less does point to the "door key cylinder switch" on the driver's side as the possible culprit - since you ruled out the remote (take the battery out to be sure). Could also be the wires that travel from the body into the driver's door through the hinge area? I'd check those first for fraying or shorts.

In '05/'06 the "door key cylinder switch" connects directly to the "power window main switch" which is in the driver's door arm rest. If '03 was the same your problem may all be behind the door panel. Possibly the cylinder switch is just worn out or one wire is shorting. If you pull the door panel you should at least be able to disconnect that switch and see if the weirdness goes away... Just an idea.

 

Is it the door actuator that send the signal to roll up/roll down the windows and set the alarm? If I disconnect the main window/lock control module in the driver door then the key control does not work for the windows.

 

For '05/06 that door key cylinder switch talks to a CPU in the power window main switch - in the driver's armrest. That is apparently one of our many black boxes.

Regarding the alarm, here are the conditions needed to arm it once the ignition is off:
When the following operation 1 or 2 is performed, the vehicle security system turns into the “pre-armed” phase. (The security indicator lamp illuminates.)
1. BCM receives LOCK signal from front door key cylinder switch or key fob, after hood, trunk and all doors are closed.
2. Hood, trunk and all doors are closed after front doors are locked by key or door lock and unlock switch. The security indicator lamp illuminates for 30 seconds. Then, the system automatically shifts into the “armed” phase

Your problems still point to the possible malfunction of that door lock switch so I think you're on the trail. Somewhere on this site is a link to service manuals. I recommend you try to grab BL, GW and maybe PG for 2003 to help you trace the error. Might also be something the dealer could diagnose by plugging your car in.

Sorry I can't give you a better answer.