Hello all! This group was helpful in recently re-routing sunroof drains in my son's 2012 G37 coupe. We cleaned and drilled out rear drains and re-routed front drains. Our next problem is an electrical one. Approximately two months ago, the power windows, power locks, sunroof, and interior light stopped working. He lives out of town so I have limited time to troubleshoot during our monthly visits. Last time he was home, I checked fuses under the hood, but all appeared good. Disconnected battery, hoping a reset would help. Finally noticed the "Room Light" fuse was burnt in the interior fuse box. This did the trick or at least I thought it did. He said it stopped working shortly after heading home. On our most recent visit, we dried out interior of car and rerouted drains then returned to electrical problem. I checked fuses again, but they seemed fine. I realized the dome light worked on startup, so I tried ACC or ON mode and EVERYTHING WORKS! Now, I am unsure if car was running or in ACC mode when we thought the room light fuse was a fix. One other note, power unlock works at all times. Maybe a safety feature? Any ideas why PW, PL, and sunroof work in ACC or ON mode but stop working when car is running?

 

As far as I know "on" mode should be the same electronically whether the engine is running or not so that's a weird set of issues.
If you don't have it, the FSM is here:
https://www.nicoclub.com/service-man...F2012%2FPG.pdf
Scroll down below the "viewing window" and you can "click here to download a copy". With some patients you should be able to trace all electrical circuits using that book.

 

Sounds like the BCM may have gotten wet/ damaged especially since you confirmed there was a active water leak.

The power locks should work whether the car is OFF, in ACC, or ON. They function independent of "key status" or "engine status" as they "always have to work." If they UNLOCK but do not LOCK, then its likely a BCM issue.

The windows/ roof should only function when the key is ON. However, after you turn the key from ON to OFF the RAP circuit is hot. RAP is the "Retained Power" circuit which provides power to the windows and roof for 30sec. OR until you open the door. This gives you time to close everything in the event you forgot while the car was ON. The windows and sunroof should NOT operate while the key is in ACC. The only thing that should operate while the key is in ACC is the radio and cigarette lighter/ power outlets. Nothing else. If they are, its the BCM.

Sounds to me the BCM got wet. There are several things you can try including disconnecting the harnesses, removing the BCM, and giving it a good once over to make sure everything is CLEAN and DRY. Including all the pins. Check all the terminals on the harness connectors as well. Also, keep in mind, though rare, there have been reports of water leaking onto the driver-side fuse block. This block also houses the ACC and IGN relays. Would not hurt to check there as well. Worse case scenario the BCM has to be replaced.

I gave you a lot to digest. Just take your time, make yourself familiar with the factory manual, and ask away. We will help the best way we can.

 

Thanks for the link. Last night I figured out this must all go back to the "ROOM LAMP" fuse. I replaced it though it wasn't burnt and PW, PL, and sunroof worked in ACC and ON position. After a while, they began to flicker and finally went out. Pulling fuse out and pushing back in had everything working again for a few minutes. This morning, nothing works.

 

The "ROOM LAMP" fuse, herein #10, directly feeds the BCM:




Given the current symptoms and being that the BCM directly controls the functions you are having issues with, it is almost certain that the BCM is the problem here.

 

Thanks! I saw this but electrical diagrams aren't my strong suit. I searched the manual for "Room Lamp", and there is a detail on the room lamp harness. As you've posted the fuse labeled "Room Lamp" seems to be linked to other, more important things. So, why label it as room lamp in the fuse box legend?

Any advice on BCM repair or replacement? I've read it has to be reprogrammed. If so, what should we expect($$) if we turn the whole project over to dealership? Also read (in only one place with very few details) that BCM can be repaired avoiding any reprogramming.

 

Do you think removing fuse and replacing is somehow restarting BCM causing it to work momentarily? Disconnecting and reconnecting the battery does not have same result. Water did leak into car around the fuse box on driver's side, and the first "Room Lamp" fuse I replaced was fried and dull gray, corroded. Any chance disconnecting battery, removing fuse, and sanding inside fuse opening with paper or emery board may solve the problem? Is there any risk in stretching the opening and no longer having a securing hold on fuse, creating a bigger issue. Thanks again!

 

With the battery disconnected I would pull the fuse block entirely and make sure there is no corrosion on the terminals, relays, and connectors. It will not be a easy task but doable.

Then, if the problems persist, you can move on to the BCM.