If you haven't known, these cars are bad for leaks in rainy weather. My car died after a bad storm before and during hurricane Helene. No crank no start. (Still trying to figure out the cause of that. I'm thinking ECM but maybe for a separate thread.) Long story short, after a couple weeks of sunny days, i was going to change out the spark plugs and coil packs, but the car decided to start. Test drove it with a semi new battery, fully charged, brakes bled out.

The problem: I parked the car and stepped out for nearly 10 minutes for a smoke break and visual inspection. The engine is still on, but I have no power to the interior. I can't turn off the car with the button, and I can't shift it to reverse or anything else. The headlight switch was set to OFF. Even in the off position, the headlights were on.

By the time I got a ride and picked up my tools, the engine had shut off, headlights still on. I assume the battery is drained so I took it out. Everything is off now and I will be charging the battery tomorrow at the nearest auto parts store since it's late.

I've never heard of this happening to anyone before so it's a weird first time situation for me. Will be checking fuses first thing when I'm free. Any suggestions will be highly appreciated.

 

BCM = Body Control Module that is located passenger side right kick panel. Remove it, open it and see if it's wet. The 2mm hole sized sunroof drains are most likely plugged up and the water is backing up the drain tubes and overflowing right over the BCM. I had the same issue, well, MOST of G owners had this issue.
Disconnect battery Negative and remove the BCM, if it's wet, dry it with compressed air or hair dryer fast! Then reinstall it and see what happens. I had good luck with my 2 BCMs and they were really flooded! make sure to clean those grounds near the BCM and fix the sunroof drains. You can find plenty of guides for that around here.

 

 

So i took out the BCM and it seems like mine is fried. Before this, I've installed a fully charged battery and got no power to the car. Would the BCM cause this? I'm asking to know if I should suspect another part since I'm in the process of taking it apart. And if I were to replace it with an exact part number, would it still need programming? Thanks for the reply. You were spot on.

 

The BCM holds the ignition and key fob codes so same part# but will need reprogramming to communicate with your ECM. Most locksmiths can do that, they can come to your house and program it for less than $200. BCM controls ignition, therefore it controls ALL parts that start the engine, including the starter relay. Bad BCM, no ignition, no start.
How do you know your BCM is fried?
How did you test for NO POWER?
I assume you installed good battery and pressed the Start button and nothing happened?
Are the dome lights on?
Red KEY steady or flashing on the gauge cluster?

 

I'm getting nothing on the inside. No lights anywhere. Headlights dont work as if the baterry isn't installed. Start button and nothing. Just one quick look at the motherboard of the BCM and you can see it's got a burnt area.

 

That's where you start. Get a used BCM with SAME part#, plug it in and you should get basic power controls like lights and ignition but no start due to programming.
IF you don't get ANY power after BCM install, check the power fuses by the battery positive terminal, the 140A and the rest below it.
Let's hope at least one of the fuses is blown, otherwise, the ECM might be in trouble.
Start with a replacement BCM first and let us know what happens.