Thank You for your response, TheAwesomeLyfe 🙂👍If your car is still under warranty, take it back to the dealer because nothing beats free repairs.
However if your warranty is up and you want to do the simple diagnostic route
1 Check the fuse panel and make sure the Fuse switch isn't off, usually you will get a warning on the cluster about it being off.
2 Check your owners manual or the label in the fuse panel and check to see if the fuse is ok.
3 On the passenger side kick panel inspect all the wiring connectors and ensure everything is plugged in correctly. the BSD system works on a CANbus network and wiring could be the culprit.
Anything else pass this point you will have to remove the sensors and replace them as the module can be faulty. There are two of them(A master and a Slave sensor) when replacing them be sure not to mix up them up
here is the service manual for the repair procedures the mechanical part is easy to do but anything this else you will need a high dollar tool to test the functions and stuff which is why the dealership warranty is the best route.
Hyundai Elantra(AD/ADa) BSD System Service Manual
Good luck, i never had an issue yet so i can't tell you the procedures in depth until i need to do a repair on my own Elantra. I hope the service manual helps and bookmark the site to your devices, Its good for if you need in depth repairs for your car.