Key Fob Stopped Working — Battery Or Reprogram?
A key fob that stopped working suddenly is almost always a dead battery, not a failed program — test that first before assuming the fob or the car system has a fault. If a fresh battery does not fix it, the fob likely needs reprogramming or has an internal fault.
The panic response to a dead fob is to assume the worst. Nine times out of ten it is the smallest possible problem.
Diagnosing a dead fob, in order
| Step | What it tells you |
|---|---|
| Replace the coin battery | Fixes the large majority of dead-fob cases |
| Try the fob very close to the car | If it works up close but not further away, battery is weak, not dead |
| Try a spare fob if you have one | If the spare works, the problem is the first fob specifically |
| Neither fob works at all | More likely a car-side receiver issue, less common |
Signs it needs reprogramming, not just a battery
- New battery installed, fob still not detected at all
- Fob works on some functions (unlock) but not others (start)
- Fob was recently exposed to water or dropped hard
Why fobs lose sync sometimes
Certain battery disconnections on the car itself, some software updates, or simply a worn internal chip can cause a fob to fall out of sync with the immobiliser system, even with a good battery. This is a reprogramming job, not a battery job.
What programming actually involves
A locksmith connects to the vehicle OBD port and re-registers the fob chip with the immobiliser system, typically 15 to 30 minutes. It does not require cutting a new key blade if the physical key already works, only the electronic side is being fixed.
Booking key fob programming
Tell us the make, model and year, and what you have already tried, battery or a spare fob. Ranges are on the prices page, and full detail is on key fob programming.