Last night I noticed that the dome light and driver's side footwell light were on even though the car had been sitting locked for a few hours. I also noticed that the open door warning light was on.

I tried slamming all doors and the trunk a few times, but to no avail. Then I just put the dome switch to OFF and called it a night. The footwell light still stayed on, though. Pretty much all other electrical things work properly, and the open door light turns off as it should when all doors are closed and the car is started.

However, after further investigation this morning I noticed that about 5 seconds after the ignition is turned off, you can hear a faint click (like a relay, or something) and the dome light, footwell light and the open door light come on.

All this even if you have not moved anywhere from the driver's seat and no doors have been touched.

Since the open door warning light is not on when the car is running, the courtesy switches on the doors and trunk work properly and this seems to be more electrical gremlin in nature.

What could possibly be causing this? And and all ideas are greatly appreciated.

 

Start Simple and work your way forwards .I would check the actualy switches in the doors that tell the car they are closed.

 

It looks to me that your problem is caused by the "Multiplex network body computer".
Those lights are controlled by the "Multiplex network body computer". The door switch is just doing a part of the function sending the open/ close signal to it.

The worst scenario is to need to fix the "Multiplex network body computer" or simply replace it but you should try resetting it removing the negative battery cable for 15 minutes or more. If this does not fix the problem, you must prepare to fix the "Multiplex network body computer".

 

Me, too. If I could find them, that is. Tried to look yesterday, but didn't see them anywhere.

Then again, I kind of doubt the door switches would be the issue since the lights are off when the ignition switch is in any other than OFF position.

Now that definitely sounds expensive. What is the location of this module? I did disconnect the negative battery cable for a few minutes but to no avail. I guess I'll try it a bit longer today and see if that helps.

 

The JDM Celsior has it under the cluster meter unit but I don't know those LH models.

 

Disconnected the battery for about 30 minutes today, but the lights are still there. Time for a replacement module, I guess... Seems like the going rate for a new one is $600+. Definitely not worth that much for me, so I'll try to find a used one from somewhere.

For the time being, I just pulled the fuse, so the battery doesn't drain. It only affects the courtesy lights and clock, anyway.

 

Oh, that's too bad for you.
Is it possible for you to take photos of the board inside of your "Multiplex network body computer"?
I might be able to suggest you what you need to replace if a used one is not easily available.
It would be better to take photos from different angles.

 

Thank you for the help, Yamae! I'll post here once I have found a replacement and maybe I'll even try fixing the old one.

IF that is causing the problem, of course...