So was at Home Depot today and on way out the car would not open. Had to get the physical key out and alarm went off when opened that way. I hit the triangle on remote and alarm stopped. The car started and drove fine. Got home and late went out to do some work on the car and same issue, it would not open. The alarm would not stop until I started the car this time. Got the spare key out and it would not work either. Later I tried again through the window of the house and car would not open, googled the issue and went out to see if anything comes up on the dash stating the key batteries need replacement. Sure enough this time the car opened fine and I saw no errors on the dash. Any ideas what this could be? I supposed batteries could be dead/going on both the remotes. I had the car just over 3 years so it feels a bit short considering I had my elantra for 6 before and remote worked fine and wife's H3 remote has been working for 15.

 

Hi. It doesnt sound like the fob batteries to me but you could change one and see if it helps. Maybe the main battery in the car?

 

thanks.... im not sure it can be the main battery as the car starts up fine.... all lights and alarm work too. But im no expert.