Come on VW. The Lexus owner left an interior light on the night before and came out to a dead car battery in the morning, meaning the power door locks didn’t work with the fob.

Like anything else relying on a battery, you car key fob can die—often at the worst time. Thankfully, these batteries are easy to replace.

The key fob is your lifeline to your car, letting you unlock the doors and set off the alarm, at a minimum, but how can you tell if it needs a new battery?

Locked out of your car because your key fob battery died? Learn step-by-step how to unlock your vehicle, start it with a dead key fob, and prevent future lockouts with this essential guide.

If a faulty anti-theft system is keeping you from using your car with waking up the whole neighborhood, there might be a few tricks you can try with your key.