Car Key Fob Not Working? What to Check First
Start with one question: does the car still start when you use the key normally? If it does, the transponder is fine and only the remote has failed — which is usually a battery and almost always the cheaper problem. If the car does not start either, that points somewhere different.
Work through these in order
Does the car start?
If yes, the immobiliser is happy and this is a remote-only fault. That narrows it immediately.
Try the second key
If the spare works normally, the first fob has failed. If both behave the same, suspect the vehicle.
Check the vehicle has power
Open the car with the blade. If there are no interior lights and no dash, the vehicle battery is the problem, not the key.
Try from very close
A dying battery shortens range before it fails. Working at 30cm but not 3m is a battery, not a fault.
Look for the emergency blade
Most proximity fobs conceal one. It gets you into the car while you sort the rest.
What each outcome means
- Car starts, buttons dead
- Remote failure. Battery, worn contacts, broken solder joint, or lost sync. Often repairable.
- Both keys behave the same
- Points at the vehicle — a receiver or antenna fault rather than the keys.
- Car completely dead
- Vehicle battery. The key is a red herring.
- Works close up only
- Fob battery discharging. Replace it before it strands you.
- Nothing at all from one key only
- That key has failed. Repair may still be possible if the transponder survived.
If the fob has been wet
Stop testing it. Repeatedly powering up a damp fob is the most common way a recoverable key becomes an unrecoverable one. Leave it somewhere dry and have it looked at.
When a failing fob becomes urgent
Most fob problems are an annoyance rather than an emergency. A few are worth acting on straight away.
- It is your only key. An intermittent fault on a single key is one bad day away from all-keys-lost work.
- The car has keyless start and you do not know where the emergency blade is.
- The engine sometimes fails to start as well as the remote failing — the immobiliser side is now involved.
- The fob has been wet. Corrosion can finish off a key days after it seems to have dried out.
Common questions
Can I change the battery myself?
On most fobs yes, and it is worth trying. Note the orientation before removing the old cell, and avoid touching the board.
If the case needs forcing, stop — cracked cases cause more problems than flat batteries.
My remote worked yesterday and not today.
Sudden total failure suggests a battery that was already marginal, a broken contact, or a key that has lost sync after being pressed repeatedly out of range.
All three are usually straightforward.
Could it be the car rather than the key?
Yes, and the spare key test is what tells you. If both keys behave identically, the vehicle is the likelier suspect.
Still not working?
Tell us what happens at each step above and we will tell you what it points at.