A key or fob that suddenly stops working usually has one specific, identifiable cause. Here’s a rundown from most common (and easiest to fix) to least.
1. Dead or Dying Fob Battery
By far the most common cause of a remote that stops locking, unlocking, or starting the car. Most fobs use an easily replaceable coin battery, a quick, inexpensive fix.
2. Worn Mechanical Key Blade
Years of insertion and turning gradually wear down the physical cuts on a key blade until it stops engaging the tumblers reliably. This is a slow decline, not a sudden failure, see our guide on signs your lock needs replacement for related warning signs.
3. Transponder Chip Failure
Even if the mechanical blade works perfectly, a failed or damaged transponder chip will prevent the engine from starting since the immobilizer won’t recognize the key. See our key fob programming explainer for how this system works.
4. Water or Moisture Damage
Fobs that go through the wash, get dropped in a pool, or sit in a damp pocket regularly can develop internal corrosion on the circuit board, often showing up as intermittent failures before it stops working entirely.
5. Interference or Signal Issues
Occasionally, other electronics or a low battery can cause a proximity fob to have a shorter range or intermittent response, without the fob actually being broken.
6. Vehicle-Side Sensor or Antenna Failure
Sometimes the problem isn’t the key at all, a failing receiver antenna in the vehicle can produce the same symptoms as a dead key.
How to Tell the Difference
If a second key (or spare) has the exact same problem, it’s more likely a vehicle-side issue. If only one key is affected, the problem is almost always in that specific key or fob.
Not sure which one it is? We can diagnose it on the spot. Call 818-249-5128. And if this is your only working key, it might be worth reading why every driver should have a spare.