Hello all it's been a while. Backstory, 08 G37S coupe is my spring/summer car. Other than that it just sits in my driveway till the snow melts. The battery dies every so often to the point of replacement every other year if I don't start it once a week. So the snow melted, battery was dead, I jumped it and now I have issues. First issue, I lost the ability to control my headlights. They turn on and off on their own even when the switch is in the off position. Second, wipers don't work neither do the turn signals or the climate control. Third and crazy one. The car wont shut off. Dash will turn off but the engine keeps running and the dash will turn off and on from time to time. I had to disconnect the battery to get it to shut off. I then replaced the battery after the original died and then it wouldn't start. Not even crank and try. Had power and control to everything else but no crank/start. Towed it to a friends shop. somehow he was able to get it started after disconnecting and reconnecting the battery. Same loss of control and engine not shutting off as I had. Has anyone have any idea whats going on or has anyone ever had this problem before? Car was in great running condition when I parked it October. Drove it more than my regular daily in September.

 

Did your friend pull codes at his shop? Sitting outside all winter is terribly hard on electrical components (and paint). Have you checked and cleaned all electrical grounds and relays like the IPDM?

 

Rule #1: Any time a car is going into "storage" or other periods of time when it is going to sit idle (untouched) for several months, ALWAYS disconnect the battery OR leave a battery tender/ maintainer attached. These cars get extremely fussy when voltages drop. Additionally, more "damage" is typically done to electrics as a result of under-voltage conditions rather than over-voltage. This is why most modern cars have a "Extended Storage Switch-" to prevent battery drain and damage to the electrics mainly while the car is being shipped.

That said, the car sat in snow and ice for several months. Any evidence of water ingress? Most of your symptoms point to the BCM which is notorious for getting wet.

Everything dkmura suggested above is spot on. Check fuses, grounds, harnesses and modules. Make sure everything is clean, tight, and free from corrosion. If you are able check for any codes post those here as that will allow us to focus in on potential problems/ solutions.

Keep us updated.