Is my car posessed?

My Elantra has a push button switch for each door that is depressed when the door is closed and released when opened. Assuming it's the same for the Sonata it sounds like one of those switches is not being depressed sufficiently and there's just enough play in one of the doors to release it. Does the dome light turn on at the same time?

As for the doors unlocking I'd definitely take the car back to the folks who installed the alarm.

Nope. But that's a good start, I can test that.

Doesn't sound like a factory part / thing issue?

Thanks :)

So some more troubleshooting - the doors only unlock when I'm stopped. And the alarm doesn't ever go off at night, so I don't believe the alarm is thinking a door is opened otherwise the alarm would be going off in the middle of the night.

Does that help with any ideas as what's wrong?

Check the switch on the door pillar. Chances are the door is dented in the vicinity of the switch contact (typically by closing the door on the seat b elt buckle), causing the door to not depress the plunger fully enough. Each time the door moves away a little due to some sort of stress, the interior lamps will come on, and if the key is in the ignition, the doors will unlo ck (to prevent locking the keys in the car since the door appears to the ca r to be open).

I'll give that a shot.. I thought though that would also make the dome light come on?

Thanks :)

So doesn't appear to be that switch. If I open the door, the dome light comes on, and since the dome light doesn't come on when this happens, it has to be something else, right?

Probably something else, then. Although it could be one of the door switch wires rubbing through on the body of the car.