A few months back a bought a 2012 g37 auto base model and after it rained for 2 days i opened the door to notice that water had gotten inside. The gutter system has already been fixed and the problem is a hole in the sunroof that I have temporarily patched. The problem is that at first the vehicle would refuse to start simply moving to on and activating all the electronics and refusing to turn them off, then after starting the traction control light would turn on. After a few minutes of driving going to AutoZone to check my Battery the car went crazy lighting up like a Christmas tree, losing power to the indicators, head unit, speedometer and tachometer, everything had stopped working for the most part with just the indicator lights and head unit going up and down In brightness. At AutoZone I got stuck again not being able to start but managed to get out with a jump.i asked for a obd2 scan since I was there with the light on and the reader didn't read any codes so we think it was a false light. When I got home and parked the vehicle it would not shut off no matter how much I pushed the button. I think it is the bcm that might have gotten wet but if you know anything please help.

 

90% of the time it is. Outside of water damage the VQ wiring just doesnt do this under any other parameters.
Nothing else in the circuit will perform like this and or will pop a fuse once it does. When it doesnt it means the corrosion line is enough to make contact and then loose it once it burns up the corrosion from an amperage draw.
When you have debris left over from what once was water you have to understand that this dried up debris can conduct electricity.

There's a few threads on what to check with the main direction being BCM and it's connector.s