It still turns the engine over the buttons just don't work cause when I lock my car at night it sets the alarm and I have to use the key on the fob to unlock the car but then the alarm goes off and I have to put the fob in the ignition to get it to shut offReplacing the battery in the fob should not make it need reprogramming the fob. What was it doing before you replaced the battery in the fob? Do the doors and trunk unlock or is just the ignition that is not letting it start. Does the engine crank? If not, it could be the battery under the hood.