Remove the key fob battery cover from your mazda remote.
Mazda 3 key fob battery replacement 2010.
Make sure the positive symbol is facing you.
Insert the new battery.
Push the metal ignition key piece back in to the fob until it clicks in to place.
Test new fob battery.
Pull out the dead key fob battery from the mazda keyless remote.
Stand near your mazda3 and press the lock or unlock buttons to test the new key fob battery.
Fold the metal ignition key back down in to the fob and double check that the parts are secure.
Push on ignition key.
The positive is on top while the negative side of the button cell battery is facing the key fob.