This is from a different thread; It worked on my new key.


After taking the batteries out, you have to re synchronize the fob.

1) with new batteries in, press the unlock button twice quickly, pointing at the car.

2) within 30 seconds, put the key in the ignition and turn to the ON position.

This re synchronizes the key to the car after the fob has lost power.

This is addressed in the owners manual.