A key fob is not working in most cases because the coin cell inside it is flat, and a new battery, clean contacts or a fresh pairing to the car brings the remote back without a new fob.
A key fob is the remote part of a car key, a small radio transmitter that locks and unlocks the doors, opens the boot and, on a keyless car, tells the car that the key is present. A coin cell powers it, a set of button switches triggers it and a paired code makes the car accept it. A fault in any of the three leaves the key fob not working. Six checks in order clear the simple cases in a few minutes, and seven causes explain the rest, five inside the fob, one in the air and one in the car. A key fob repair costs from £25 in Liverpool, takes 15 to 30 minutes at the car and keeps the fob that the car already recognises.
A sudden failure, an unresponsive fob, a reset, driving with a dead fob, cold weather, two dead fobs, the not detected message, a short range, a fob that works sometimes, a wet fob, one dead button, the battery type, reprogramming, the life of a fob and the car make raise fifteen further questions.
The list below gives four key takeaways on a key fob not working.
- A flat coin cell is the most common cause, and a new CR2032 costs £2 to £5.
- A spare fob that works places the fault in the first fob, and two dead fobs place it in the car.
- A fob that fails straight after a battery change has the wrong cell, a bent contact or a lost pairing.
- An auto locksmith repairs the buttons, the case and the circuit board at the car, so a new fob is the last step and not the first.
Which 6 checks fix a key fob?
Six checks fix a key fob not working in most cases, and the spare fob and a new coin cell settle more faults than the other four together. The list below gives the six checks in order.
- Try the spare fob, since a spare that works places the fault in the first fob.
- Fit a new coin cell of the type printed on the old cell, usually a CR2032, with the plus side facing the same way.
- Clean the battery contacts and the rubber button pad with a dry cloth, and lift a flattened contact gently.
- Move the car or the fob away from masts, chargers and other transmitters, then press the button again.
- Press the unlock button four times beside the driver door, which pairs the fob again on many cars.
- Charge a car battery below 12 volts, since the receiver in the car requires power to answer the fob.
The six checks take about ten minutes and cost the price of one coin cell. A key fob that stays dead after all six has a fault on the circuit board or has lost its pairing, and both are put right at the car.
Why does a key fob stop working?
A key fob stops working because the fob has no power, sends no code or sends a code the car no longer accepts. The list below gives seven causes in order of frequency.
- A flat coin cell cuts the range first and then stops the remote, after about 3 to 4 years of use.
- Worn button switches or a split rubber pad leave a press that never reaches the circuit board.
- A cracked solder joint or a loose battery clip, usually after a drop, breaks the power to the board.
- Water from rain, a wash or a spill corrodes the tracks on the board.
- A lost pairing, often after a battery change or a long spell with a flat cell, leaves the car ignoring the code.
- Radio interference near masts, chargers and busy car parks blocks the code for a moment.
- A flat car battery, a blown fuse or a failed receiver leaves the car unable to answer any fob.
The first five causes sit inside the fob, the sixth sits in the air and the seventh sits in the car. A key fob with a flat cell gives a warning first, with a shorter range and buttons that take two or three presses. A new battery that changes nothing is the next thing drivers meet.
Why does a new fob battery not help?
A new fob battery does not help where the cell is the wrong type, sits the wrong way up or the fob lost its pairing while the cell was out. The list below gives five reasons a key fob stays dead after a battery change.
- The cell is the wrong type, since a CR2025 is thinner than a CR2032 and loses contact in the holder.
- The cell sits upside down, with the plus side against the wrong contact.
- A contact was flattened or a clip was snapped as the case came apart.
- The cell is old stock and reads under 3 volts on a meter.
- The fob lost its pairing while the cell was out, and the car no longer accepts the code.
The first four reasons are put right at home in a minute. The fifth requires the fob to be paired again, by the button sequence on some cars and with diagnostic equipment on others. A key fob that passes all five has a fault that was never the battery, and the symptom shows which one.
Which symptom points to which fob fault?
Each symptom points to one fob fault, and a range that shrinks over weeks points to the coin cell while a sudden stop points to damage or pairing. The table below matches seven symptoms of a key fob not working to the likely fault and the fix.
| Symptom | Likely fault | Fix |
|---|---|---|
| Range drops to one or two metres | Weak coin cell | Fit a new cell |
| One button is dead and the others work | Worn switch under that button | Button repair |
| Buttons work only with a hard press | Worn rubber pad or dirty contacts | Clean the contacts or renew the pad |
| Fob dead after a drop | Cracked solder joint or loose battery clip | Circuit board repair |
| Fob dead after water | Corrosion on the circuit board | Dry the fob and have the board assessed |
| Fob dead straight after a battery change | Wrong cell or lost pairing | Check the cell, then pair the fob again |
| Both fobs dead on the same day | Car battery, fuse or receiver | Test the car, not the fob |
Rows one to six are faults inside the key fob. Row seven is a fault in the car, and one test separates the two.
Is the fob or the car at fault?
The spare fob shows whether the fob or the car is at fault, and a spare that works clears the car in seconds.
A spare that works leaves the first key fob as the only suspect. Two fobs that fail together point to the car, where a battery under 12 volts, a blown central locking fuse or a failed receiver stops every fob at once. Dim interior lights and a slow starter confirm a weak car battery.
A key fob also holds two separate parts, the remote behind the buttons and the transponder chip that the car reads before the engine runs. Dead buttons with an engine that still runs on the key leave the chip healthy, so only the remote side is repaired. A keyless car that shows a key not detected message has a fob with too little power to answer, and the same six checks apply.
Who repairs a faulty key fob?
An auto locksmith repairs a faulty key fob at the car, and a main dealer replaces the whole fob in place of a repair.
Three routes exist. An auto locksmith opens the fob beside the car, renews the buttons, the case or the damaged track, pairs the fob and tests it on the vehicle. A postal repair service mends the fob on a bench and leaves the car without that fob for several days. A main dealer orders a new fob, which costs the most and takes the longest. A key fob repair in Liverpool from ADC Locksmith Liverpool starts at £25 with no call out fee and no VAT, and takes 15 to 30 minutes on site. Craig Evans holds SERMI approval, the accreditation for access to the security data of the car maker, which pairing a fob through the diagnostic port requires. A circuit board that is burnt or corroded through is the one case where a new fob is supplied and programmed in the same visit.
What does a key fob repair cost?
A key fob repair costs from £25 for a battery replacement and from £45 for a button or casing repair in Liverpool, and a coin cell fitted at home costs £2 to £5. The table below compares five jobs by price.
| Job | Price | Who does it |
|---|---|---|
| Coin cell fitted at home | £2 to £5 | The driver |
| Battery replaced and fob tested at the car | From £25 | ADC Locksmith Liverpool |
| Button or casing repair | From £45 | ADC Locksmith Liverpool |
| Circuit board or water damage repair | Quoted once the fob is open | ADC Locksmith Liverpool |
| Whole fob replaced and programmed | The highest price of the five | Auto locksmith or main dealer |
A repair keeps the circuit board and the chip that the car already recognises, which is why a key fob repair costs a fraction of a new fob. ADC Locksmith Liverpool gives a fixed price on the call, before travel.
How do drivers keep a key fob working?
Five habits keep a key fob working, and a coin cell changed at the first drop in range prevents most failures. The list below gives the five habits.
- Change the coin cell at the first drop in range, or every two to three years.
- Keep the fob dry, and leave a wet fob unpressed until it has dried.
- Fit a cover over a fob with a worn or split button pad.
- Press the spare fob once a month, so a flat spare is found before it is wanted.
- Carry the fob outside tight pockets, where held buttons drain the cell.
A key fob that asks for a second press is giving the early warning. A battery or a button repair at that stage costs less than a fob that fails away from home.
What else do drivers ask about key fobs?
Drivers ask about key fobs in fifteen further questions on a key fob not working. A sudden failure, an unresponsive fob, a reset, driving with a dead fob, cold weather, two dead fobs, the not detected message, a short range, a fob that works sometimes, a wet fob, one dead button, the battery type, reprogramming, the life of a fob and the car make are the fifteen topics, and the questions below answer each one.
Frequently asked questions
Why did the key fob suddenly stop working?
The key fob suddenly stops working in most cases because the coin cell has gone flat.
A drop, a soaking or a lost pairing explains a fob that fails on a fresh cell.
How is an unresponsive key fob fixed?
An unresponsive key fob is fixed in most cases with a new coin cell and clean battery contacts.
A fob that stays dead goes to an auto locksmith for a board repair or a fresh pairing.
How do drivers reset a key fob?
Drivers reset a key fob on many cars by pressing the unlock button four times beside the driver door.
The guide to a car not unlocking with the key fob gives the ignition method.
Does a car drive after the key fob dies?
Yes, a car drives after the key fob dies, since the chip that the car reads draws no battery power.
A backup position lets drivers start a car with a dead key fob on keyless models.
Why is the key fob not working in cold weather?
The key fob is not working in cold weather because a cold coin cell delivers a lower voltage.
A weak cell that copes in summer fails near freezing, and a new cell cures it.
Why did both key fobs stop working?
Both key fobs stop working together where the fault sits in the car and not in either fob.
A flat car battery, a blown fuse and a failed receiver are the three usual causes.
What does key fob not detected mean?
Key fob not detected means the keyless car senses no fob inside the cabin.
A flat coin cell is the usual cause, and a phone against the fob is the second. The key not detected message has its own guide.
Why does the key fob work only close up?
The key fob works only close up because a weak coin cell shortens the range.
A range that stays short on a new cell points to the board. The guide to a key fob range getting shorter gives the tests.
Why does the key fob work only sometimes?
The key fob works only sometimes where a worn button switch or a loose battery clip breaks the contact.
A press that works on the second or third attempt is the early sign.
Does a wet key fob work again?
Yes, a wet key fob works again in many cases where the fob is left unpressed and dries fully.
Corrosion that has reached the tracks calls for a board repair or a new fob.
Why is one button on the key fob not working?
One button on the key fob is not working because the switch under that button has worn out.
The switch is renewed on the board, and the other buttons stay as they are.
Which battery does a key fob take?
A key fob takes a 3 volt coin cell, most often the CR2032, and the type is printed on the old cell.
Several places get a car key battery replaced for about £5 to £15 fitted.
Does a key fob require reprogramming after a battery change?
No, a key fob does not require reprogramming after a battery change on most cars, since the pairing sits in permanent memory.
A fob left without a cell for months loses its place in the code and is paired again.
How long does a key fob last?
A key fob lasts as long as the car in many cases, and the coin cell inside lasts about 3 to 4 years.
The buttons and the case wear first, and both are renewed without a new fob.
Does the car make change why a fob fails?
No, the car make does not change why a fob fails, since every make relies on a coin cell, buttons and a paired code.
The make changes the pairing method, which on many models requires diagnostic equipment.
Based in Liverpool and still stuck?
ADC Locksmith Liverpool repairs, programs and replaces car keys at the roadside across Liverpool and Merseyside, usually on the same day. Craig Evans holds SERMI approval and a 5.0 rating from 341 Google reviews. A call to 07731 544220 brings a fixed price before Craig travels.
Call 07731 544220