1998 Hyundai Elantra 1.8L automatic.The airbag warning light came on.Does anyone know what could cause this?

Well, if you get in an accident and the airbag deploys it will come on. I assume that's not the case though. Take it to a dealer so they can check it and reset the light. I'm not sure what the problem could be, but you don't want your airbag deploying when it shouldn't.

On many chrysler products the cause was a defective clock spring (no joke) and on my 1988 750 I had a bad clock spring. Unplugging the air bag module without disconnecting the battery will also set off the light and Advance or Auto Zone may be able to scan and reset for you (free) so ask them and if they can help ypou it will also code out the problem.