I have a brand new, or it was brand new when I bought it, 2019 Elantra SE. As basic as you can get and was dismayed to learn that my first ever new new car did not come with heated seats. Oh well my son bought a heated seat kit for me at the time I bought the car and 2 years later my daughter helped me install the kit.

The only problem was that the seats do not turn off when I turn off the car and so I must remember to turn off the seats when I turn off the car. Of course the days on which you need heated seats are the last days you want a dead battery.

When I went for state inspection a couple of weeks ago, the ODB plug was getting no power. Fortunately the mechanic figured out how to run power to the plug from the batter and was able to complete the inspection, but sent me to Hyundai dealier to fix ODB issue.

According to mechanic at dealer, the thing we plugged into the heated seat fusebox, where the fuse box indicates heated seat for front is supposed to go was pulling power from the ODB plug. so he moved the bridge or jumper on the special plug thing we were using for the heated seats to the other spot and the ODB plug got power, but heated seats no longer did.

I decided I would try and fix the heated seats issue. I moved the heated seats plug to the sunroof fuse. - nope still getting power with car turned off and no key in ignition. I thought I would have a look at the one of the only other possible 20 amp slots in the fuse box just to see. Door locks. No power at all when I plugged in the heated seats thing. So I put the heated seats plug back into the spot designated for front heated seats and returned the 20amp fuse to the door locks spot. Doors no longer registers the key fob and do not switch on and off with switches in doors or from driver's door. Nothing.

I tried resetting by holding door lock key on fob down for 1 second then putting key in ignition and turning the car on - Internet advice. No joy.
Not sure what else to do.

I did purchase and download a vin specific PDF for my car - very expensive, but it's so long and dense I am not sure where to find or how to read if I do find it the wiring diagram. I believe the heated seat issue has something to do with the other fuse box in the engine compartment, but after that I am lost and have no idea what to do, Kind of intimidated after wrecking the locking system on the doors to try anything else.

 

There is a lot here.
Can you disconnect the heated seat feature an see if the problem goes away. At least nothing was damaged . Before reconnecting the new feature , check with the seller and see they have any suggestions.