Car used to sound an "alarm" when I left the car with the lights still on. No More. Why?

you're going to have to contact the dealership on the restoration of the default properties...tho you could experiment by disconnecting the black cable leaving it OFF while you release any latent charges on any devices that use a memory.....then replace the cable and reset the clock...perhaps this "default" setting will find itself...easier than goin' to the dealership~

It MIGHT be something as simple as changing it back to the factory default settings for this "alarm", but I'd suggest looking at the Owner's Manual to see what information may be there about this, BEFORE you start fiddling around with wires under the hood. Until you get it fixed, you should be like man (a guy with OCD..lol) and check 12 times that you turned the lights off before you leave your car!

I always leave my lights on by mistake on bessie, because knob-shine kid who owned the truck jerked out all chimes, buzzers, the driver's door switch and horn all completely disabled...leave my lights on by accident ALL the time with this truck...would someone come and install a door switch and lights chime....will try to make it worth your while~installed one of those cheapy ahh-ooo-gah horns as the original could not be located~

disconnecting the main ground isn't "fiddling with wires" it is resetting to default~

Keep in mind, Judge ..that not everyone is proficient as you might be with "disconnecting the main ground" or several other areas under the hood. We've got MANY people here who wouldn't even to begin to know (or feel comfortable with) doing some of the things you recommend. A LOT of people (I'm not one of them) just hop in their car, turn the key and hope for the best.....Just sayin'

you're right REX....always with the goddamn condescension....not intentional, but do believe that if you're goin' to a car site...you're gonna deal with car guys....also you could look at it like this.....if a man put it together....a man can take it apart....well yeah, but what if a ROBOT put it together???what then huh? what if they used plastic weld-in-place fasteners....what are we supposed to have plastic rivets in our arsenal? No, they are not meant to be fixed....cannot begin to show my sense of rage at hyundai....takin' the pants off of the falllen hero~

...also cars these days just look like charging RHINOS....enough of kindly sharing your space with a fun-to-look at and non-intrusive vehicle that isn't trying to dominate everything and block your view while taking up to dangerous speeds because "it can handle it" with TCS and ABS....you can't win~....drinkin' a slurpie while talkin' on the cellphone while yellin' at the kids...some people around here....just stay safe here behind my computer~

https://www.youtube.com/watch? v=uuDeEArJ8NQ&list=PL53C9C833D51A4530

the workers there no how to stand clear....there really are quite a few assembly hours to make one of these NO wonder they are KInd0spensive~

It's a rubber covered plunger switch on the inside of the door jam to blame. The seatbelt can get jammed up there and knock it out of whack. Worst case scenario, you can swap the passenger side switch with the driver side switch. Just a phillips screwdriver and a pinch connector. Be careful of the spring and be careful not to lose the connection wires inside the frame!