I have a 2010 Mazda 3. Today for some reason unknown to me, the keyless entry stopped working as it normally does. Before today, if I clicked the lock button on the key fob, the parking lights would flash and if I pushed it again, the parking lights would flash again and the horn would sound. When I unlocked it, the parking lights flashed twice. Now, when I push the lock button, the doors lock but the parking lights don't flash and the horn won't sound, but the lights still flash twice when I unlock it. What caused this?

 

your fob may need to be reprogrammed or the transponder that picks up your fob's signal is bad

 

I found the problem. My rear driver-side door was slightly ajar because I had a backpack in the floor and the plastic adjustable piece on the strap was caught in the door, keeping it just enough ajar to effect the way the keyless entry operates. Once I pushed it back inside and closed the door again, it started working normally.