Ok guys I have a slight problem... When I start my 05 G35 and the door is open everything is fine but as soon as I close my door the car will start that annoying beeping sound for about 5 secs and you can open the door and shut it again and it will start beeping again. My battery dies super quick now I'm sure I need a new one at this point but idk if this might have anything to do with it. Does anyone have any insight?

 

there should be a button/pin that gets pushed in on the frame of the car that gets pushed in whene you close the door that might be broken or loose .

 

Also check the trunk. My car will sometimes beep and tell me the trunk is ajar... but ONLY after a hard rain.

 

Likely your hood pin not getting pushed down all the way or battery corrosion/bad battery.

My 07 coupe did it the day after I bought it this July, dealer disconnected the sensor which stopped the problem. Ended up putting a spacer under it to raise it up 1/3 inch and reconnected it. Problem free for the last 4 months (knock on wood)