I have a 2001 Galant DE with about 125,000 miles on it. I bought it new just after it rolled off the truck with only 1 mile on the odometer. There have been very few problems over the years and it’s been passed from wife to daughter to grandson. Now, it’s developed a confusing problem. When you turn on the lights with the engine off, the MFI relay starts buzzing. If you turn them on with the engine running, everything’s fine. If you turn off the lights, then kill the engine, everything’s fine. If you kill the engine, then turn off the lights, they’ll come back on at some point.

I tried swapping a couple of relays, but nothing change. A different battery didn’t change anything either.

Any idea what could be the problem? I'm not sure whether I should call a mechanic, or an exorcist.