Updated · Keys and lockouts
Signs the fob battery is fading
The first clue is range. You have to walk closer before the doors respond, or press the button two or three times. Push-button cars may show a low key battery message on the dash, or pause before they detect the key when you press start.
- Shorter unlock range than before
- Buttons that work only some of the time
- A low key battery message on the dashboard
- A key not detected warning when you try to start
Get the right battery
Most fobs take a flat lithium coin cell. The size is printed on the old battery, as a code like CR2032, CR2025 or CR2016, and the owner's manual lists it too. Those look almost identical but differ in thickness, so match the code exactly.
Buy a fresh pack. A cell that has sat in a drawer for years may already be weak.
How to change it
Work over a table, not over the car seat, so tiny parts don't disappear into the gaps.
- Slide out the metal backup key if your fob has one; its slot is often where the case opens.
- Twist a small flat screwdriver or a coin gently in the seam to separate the halves.
- Note which side of the old battery faces up, usually the side marked +.
- Press the new battery in the same way, handling it by the edges.
- Snap the case shut all the way around, then test lock, unlock and start.
If the fob still won't work
Check that the battery isn't upside down and that the case clicked shut on every side. A bent metal contact inside can also break the connection; nudge it back gently.
In most cars the fob keeps its programming through a battery change. If it still won't respond, a dealer or an automotive locksmith can check whether it needs programming again. That's not a service we offer.
Getting in and starting with a dead fob
A dead fob doesn't have to strand you. The backup key opens the driver's door; on many cars the keyhole hides under a small cap at the end of the handle that pops off from below. Inside, many push-button cars will start if you hold the fob right against the start button or set it in a marked slot. Your owner's manual shows the exact spot.
If the car still won't start with the fob against the button, the problem may be the car's own battery. A dim dash and clicking point that way, and a jump start is the next step.