Car wont start.

Hello, the key fob does not need to be programmed when changing a battery in the fob. The fob itself doesn't get programmed; the vehicle gets programmed to the fob. I would suggest starting the diagnostic process by checking your engine's battery. If the battery is low in charge, then the engine will not crank and start. If this is the case, the battery should be checked for state of charge and the ability to sustain a load. If all tests good here, then the starting and charging system should be checked for faults. If the battery is discharged but when charged sustains a load and charge satisfactorily, then there may be a parasitic draw causing loss of battery power over time. If you need assistance testing the vehicle: https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.