Key Fob Stopped Working
When a key fob stops working, the cause is usually simple and cheap. By far the most common is a dead coin-cell battery inside the fob, which gradually loses charge over a few years. If a fresh battery doesn't fix it, the fob may need reprogramming, a fuse for the keyless/locking system may have blown, or the fob's buttons or the car's receiver may have failed. If both your fobs stop working at once, the problem is more likely in the car than in the fobs.
Trouble codes you may see
If you scan the car, these are the OBD-II codes most often behind this symptom:
Common causes
- 1
Dead fob coin-cell battery
The most common cause. The small lithium coin battery (e.g. CR2032) weakens over a few years until it can't send a signal. Replacing it is a quick, inexpensive fix.
- 2
Fob needs reprogramming
Some vehicles require re-syncing the fob after a battery change, a car-battery disconnect, or buying a new fob, so the receiver recognizes its rolling code again.
- 3
Blown fuse for keyless entry / door locks
Most cars have a fuse for the central locking or keyless system. A voltage spike or moisture can blow it, killing fob function even with a good battery.
- 4
Worn buttons or internal fob damage
Cracked cases, water intrusion, or worn button contacts can stop the fob transmitting. A single non-working button often points here.
- 5
Failed receiver or antenna module in the car
Age, water intrusion, or electrical faults can disable the car's receiver. Suspect this when both fobs fail together but the fobs themselves test fine.
- 6
Radio-frequency interference
Nearby transmitters, chargers, or being too far from the car can temporarily block the signal. Stepping closer or moving away from interference often restores function.
What to do
This isn't a safety issue and the car will still drive, so start with the cheapest fix: replace the fob's coin battery and try again, using the physical key blade or backup unlock method to get in meanwhile. If a new battery doesn't help, check the keyless/door-lock fuse and try your spare fob to isolate whether it's the fob or the car. If both fobs fail, have the receiver and reprogramming handled by a locksmith or dealer.
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