4Keys Locksmith
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My key fob stopped working. What actually failed?

The remote, the immobilizer and the coin cell are three different systems in one piece of plastic. Work through the checks below and you will know which one broke before anybody quotes you a price. Some of them cost nothing to fix.

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4Keys auto locksmith technician testing a car key fob and its coin cell battery at the vehicle

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Three different jobs get called "my fob is broken"

Replacing a coin cell, re-pairing a fob you still have, and programming a brand new fob are three separate jobs with three separate prices. Nobody can quote you honestly until the symptom is classified, so classify it first. The checks below take about fifteen minutes and several of them are free.

Smart key and fob serviceSee the full price list
Check This First

Six checks to run before you pay anyone

In the order a technician would run them. Stop as soon as one of them answers the question.

  1. 1

    Read the number on the coin cell before you buy one

    Open the fob and read the cell. Most are CR2032, but CR2025, CR1620 and CR1616 are all in use, and a thinner CR2025 sitting in a CR2032 seat makes intermittent contact that looks exactly like a failing fob. Note which face is positive before you pull the old cell out. If a fresh cell changes nothing, look at the contact spring and the solder pads under it: a bent spring, a green corroded terminal or a cracked solder joint on the battery pad kills a fob that is otherwise perfect. On some vehicles the fob needs a re-sync from the driver seat after it loses power, and the procedure is in the owner manual under key battery replacement.

  2. 2

    Test the second fob, because that is the branch that matters

    If the spare works, the fault is inside the first fob and the car is fine. If both fobs are dead at the same time, the problem is almost certainly not the fobs. Two independent transmitters do not fail on the same afternoon. Look instead at the keyless entry fuse in the interior fuse box, at the RKE receiver module that listens for the fob, at the Body Control Module, or at an aftermarket alarm spliced into the factory wiring, which is a common cause in cars that changed owners.

  3. 3

    Get inside with the emergency key blade

    Almost every smart fob hides a mechanical emergency key blade released by a catch on the side or the back of the housing. Most door handles then hide the cylinder itself under a small cap or trim cover on the driver side, usually popped off with the blade or a trim tool. You do not need a locksmith to open a door you already have the blade for, and a shop that tells you otherwise is selling you a lockout you do not have.

  4. 4

    On push to start, use the backup start position

    A dead coin cell does not stop the car from starting, because the immobilizer transponder inside the fob has no battery: it is energized by a coil antenna in the vehicle. That coil is the backup start position. On many Toyota and Lexus models you touch the fob to the START button, on many Honda models you hold the fob flat against it, and on several Nissan and Infiniti models you press the button with the fob itself. Some makes put the coil on the steering column or in the center console instead. The exact instruction for your car is in the owner manual, under the section on a discharged key battery.

  5. 5

    Watch the security light to split remote from immobilizer

    Doors dead and engine fine means the radio side failed: Remote Keyless Entry, the one-way transmitter that runs on the coin cell, at 315 MHz on most North American vehicles and 433.92 MHz on European and some newer ones. Doors fine and engine dead means the immobilizer side failed: the transponder chip is no longer being recognized, the security or key shaped light on the cluster behaves abnormally, and the engine may crank and die within a second as fuel is cut. Solid versus flashing means different things on different makes, so report what you see rather than what you think it means.

  6. 6

    Take everything else off the keyring, then try again

    On Ford vehicles with PATS, code B1602 is a partial key read, and the documented causes include other transponder keys and large metal objects riding on the same ring. B1600 is no key read at all and B1601 is an unprogrammed key. Generic code P0513 is Incorrect Immobilizer Key. Stripping the ring down to the one key costs nothing and occasionally ends the whole problem. Same logic for location: if the fob works at home and dies in one parking garage, that is radio interference, not hardware.

Which System Failed

Your fob shares a shell with two separate systems

The remote radio and the immobilizer are independent. Knowing which one quit is the difference between a battery and a programming job.

The remote radio failed

Buttons do nothing, or only work a foot from the car. Causes, roughly in the order we find them: the coin cell, a corroded battery contact or cracked solder joint, a worn carbon button pad under the rubber, a blown keyless entry fuse, a failed RKE receiver module, an aftermarket alarm intercepting the factory signal, or local RF interference. The car still starts normally with the key or the backup start position.

The immobilizer failed

Doors may still work, but the engine will not run. The transponder chip is not being recognized, the security light behaves abnormally, and the engine can crank and then die as fuel is cut. This is Ford PATS, GM Passlock and PASS-Key III+, Chrysler Sentry Key and SKIM, or the Toyota and Lexus Smart Key System refusing to authorize a start. It is a programming job, not a battery.

Nothing failed at all

A dead coin cell blocks the buttons and the proximity wake, and nothing else. The emergency key blade still opens the door, and the backup start position still starts the engine, because the transponder is passive and draws its power from the vehicle. So the test is simple: if the blade opens the door and the fob in the backup position fires the engine, nothing is broken except a battery. Check that before you pay anyone, including us.
The Three Jobs

Same complaint, three different jobs

Classify the symptom, then read the price. Working the other way round is how people end up buying hardware that was never the problem.

Replace the coin cell

A battery swap, plus a re-sync on the vehicles that need one after power loss. It is the cheapest outcome and the one we check first on arrival. We do not publish a price line for a coin cell on our price list, so no number is quoted for it here. We will not invent one.
No published price line

Re-pair or copy a fob you still have

The fob exists and is physically intact, so no new hardware is needed: the existing chip ID is either re-registered or cloned onto a spare. Cloning copies the ID your car already trusts and the vehicle key count does not change. Registration writes a new ID into the immobilizer and the count goes up. They are not the same job.
Duplication $100 to $250

Program a brand new fob

The fob is gone, drowned or cracked open, so a replacement is matched by FCC ID and OEM part number, both printed on the housing, then written into the immobilizer through the OBD-II port. Tier depends on the system: domestic transponder, smart proximity, luxury European, or all keys lost when no working key is left.
Smart proximity $250 to $500
Rule Out The Fob First

Two dead remotes is not two dead batteries

A key fob is a one way radio transmitter. It shouts a rolling code and walks away. The car has to be listening, and the listener is a separate part: an RKE receiver module wired to the Body Control Module. Those are two different components, and a shop that uses the names interchangeably is guessing.

That matters because the failure points backwards. When one fob dies, the fob is the suspect. When both die on the same day, the transmitter side is statistically cleared and the receiving side is the suspect: a blown keyless entry fuse, a failed receiver, a BCM fault, or an aftermarket alarm module that was spliced into the factory wiring by a previous owner and has now quit. Buying a third fob at that point fixes nothing, and you will have paid for programming that cannot be tested.

Range loss is its own signature and it is worth reporting precisely. A fob that works at two feet and not at twenty is not dead. That is a weakening cell, a corroded terminal, a cracked solder joint on the battery pad, a worn carbon pad under a button, or a damaged antenna trace in the board. Several of those are repairs, not replacements.

We also work on vehicles most key pages skip. Work vans and trucks are part of the same skill set, and we cut and program keys and remotes for them, including Freightliner Sprinter and GMC Savana vans. Ask on the phone and we will tell you straight whether your specific chassis and year is one we can do on site.

If the diagnosis lands on the immobilizer rather than the remote, the work is described on Car Key Programming, and if no working key is left at all it becomes an all keys lost job. The Spanish version of this page is at El control de mi carro no funciona.

Real Fleet

The vehicles we actually do this work on

Model years below are the ones our technicians have worked on, not a catalog. An early 2000s car with a separate alarm remote and a metal blade is a different job from a push to start proximity fob, and this list spans both.

ModelYearsKey TypeWhat We Do
Honda Accord1998-2019Transponder blade key with a separate remote on the early years, integrated remote head key later, proximity smart fob on the newest trimsCoin cell and contact repair, fob re-pairing, new fob programming, all keys lost
Toyota Corolla1999-2018Blade key with a separate remote on the early years, remote head key later, Smart Key proximity fob on higher trimsCoin cell and contact repair, fob re-pairing, new fob programming
Honda Civic2010-2022Remote head key on the earlier years, proximity smart fob on later trimsFob re-pairing, new fob programming, all keys lost
Honda CR-V2003-2014Blade key with a separate alarm remote, or an integrated remote head key depending on the year and trimSeparate alarm remote replacement, fob re-pairing, new key and fob programming
Acura TL2004-2009Blade key plus a separate alarm remote on many cars of this generationAlarm remote replacement and programming, transponder key cutting and programming
Toyota Camry2008-2020Transponder blade key with a separate or integrated remote, Smart Key proximity fob on higher trimsCoin cell and contact repair, fob re-pairing, new fob programming, all keys lost
Hyundai Sonata2008-2017Blade remote key on the earlier trims, proximity smart key on later trimsFob re-pairing, new fob programming, all keys lost
Nissan Rogue2011-2023Proximity Intelligent Key on most trims, blade remote key on early base trimsCoin cell and contact repair, new fob programming, all keys lost
Nissan Sentra2010-2025Blade remote key on base trims, proximity Intelligent Key on higher trimsFob re-pairing, new fob programming, all keys lost
Volkswagen Jetta2007-2020Flip blade remote key on most trims, proximity fob with KESSY on higher trimsFlip key remote repair, new fob programming, all keys lost
Chevrolet Silverado2015-2023Flip blade remote key or proximity fob depending on the year and trimFob re-pairing, new fob programming, all keys lost
Ford F-1502012-2020Remote head transponder key on the earlier years, proximity fob with push to start on later trimsPATS diagnosis, fob re-pairing, new fob programming, all keys lost
Ford Explorer2009-2020Remote head key on the earlier years, proximity fob on later trimsPATS diagnosis, new fob programming, all keys lost
Lexus RX 3502013-2024Smart Key proximity fob with push to startCoin cell and contact repair, new fob programming, all keys lost
Volkswagen Atlas2024-2025Flip blade remote key on base trims, proximity fob with push to start on higher trimsNew fob programming, spare fob added, all keys lost
Freightliner Sprinter 25002016Transponder key with the remote buttons built into the key headWork van key cutting and programming, remote replacement, all keys lost

Combustion vehicles only. Your exact trim decides whether the car uses a remote head key or a proximity fob, so read the FCC ID off the back of your fob when you call and we will confirm the tier before dispatch.

If no working key is left, expect to prove the car is yours. A locksmith who does not ask is the warning sign.

On an all keys lost job we write a new key ID into your immobilizer, which is exactly what a thief would want done. So before any tool touches the vehicle we ask for the title, the current registration, or an insurance card in your name, plus a photo ID that matches it. If a locksmith is willing to program a key to a car without checking any of that, they will do it for the next person too, and the next car might be yours.

Lost Car Key ReplacementHow to verify a locksmith in 60 seconds
Published Tiers

What each of the three jobs actually costs

These are the published lines that apply once the symptom has been classified. A coin cell is not on this list because no price line exists for it, and we will not print a number we have never set.

ServiceDay RateNight / Weekend
Car key duplication (transponder or fob)Copy made from a key that still works$100 - $250+$120 night
Car key programming (domestic transponder)Toyota, Honda, Ford, Chevy, Nissan, Hyundai, Kia$150 - $250+$50 night
Smart proximity key programmingPush-to-start fobs on domestic and Asian makes$250 - $500+$50 night
Car key programming (luxury European)Mercedes, BMW, Audi, Range Rover, Porsche, when a working key still exists$250 - $450+$50 night
All-keys-lost programmingFull new system pairing. The spread is the make: a Toyota key and a Ferrari key are not the same job$200 - $1,000Varies by vehicle

*Prices shown are reference only. Final cost varies based on the complexity of the service, the specific hardware involved, the vehicle make, model and year, and the time of service. We provide an exact phone quote before our technician is dispatched. Automotive prices depend on the make, the model and the year of the vehicle. A key for a Toyota and a key for a Ferrari are not the same job, and the ranges above reflect that spread. The dispatcher confirms the exact total on the phone before a technician is sent.

FAQ - Key Fob Not Working

Got questions? We have answers. If you don't see your question below, call us anytime - we're available 24/7.

Three things, in order. First confirm the cell size and orientation: a CR2025 dropped into a CR2032 seat is thinner and makes intermittent contact, and a cell installed upside down does nothing at all. Second, look at the contact spring and the solder pads under the battery: a bent spring, a corroded terminal or a cracked solder joint is a common fob killer and it is a repair, not a replacement. Third, some vehicles want a re-sync from the driver seat after the fob loses power, and that procedure is listed in the owner manual under key battery replacement. If all three check out, the fault is likely in the vehicle receiver rather than the fob.
Possible, but unlikely, and that is the useful part. Two independent transmitters rarely fail together, so the evidence points at the receiving side: the keyless entry fuse, the RKE receiver module, the Body Control Module, or an aftermarket alarm that was spliced into the factory wiring and has failed. Check the interior fuse box first because it costs nothing. Buying a third fob before ruling this out means paying for programming on a car that still cannot hear a fob.
The radio side, which is Remote Keyless Entry. It is the one way transmitter powered by the coin cell in the fob, and it handles lock, unlock, panic and trunk. The immobilizer is separate and is clearly still working, because your engine runs. This split matters for price: a fob radio problem is often a cell, a contact or a duplication job at $100 to $250, while an immobilizer problem is a programming job.
No, it is the opposite branch. That is the immobilizer refusing to authorize a start, which is Ford PATS, GM Passlock and PASS-Key III+, Chrysler Sentry Key and SKIM, or the Toyota and Lexus Smart Key System, depending on what you drive. A scan tool reads the stored code. The generic one is P0513, Incorrect Immobilizer Key. On Ford PATS, B1600 is no key read, B1601 is an unprogrammed key and B1602 is a partial key read. Domestic transponder programming runs $150 to $250 and smart proximity programming runs $250 to $500, set by the make, the model and the year.
Run the ladder. Swap the coin cell for a known good one of the correct size. Test your spare fob on the same car. Pull the emergency key blade and open the door by hand. On a push to start car, hold the fob in the backup start position and see if the engine fires. Then watch the security light. If the spare works, the first fob is at fault. If the blade and the backup start both work, nothing is broken except a battery or a contact. If neither fob does anything and the fuse is intact, the receiver in the car is the suspect.
Read it off the old cell rather than guessing, because the number is printed on the face. CR2032 is the most common, but CR2025, CR1620 and CR1616 are all in current use and the two 20 mm cells look identical until you measure thickness. A CR2025 will physically sit in a CR2032 holder and then drop contact over speed bumps, which reads as a fob that works sometimes. Note which side faces up before you remove the old one.
Use the backup start position. The immobilizer chip inside the fob has no battery of its own: a coil antenna in the vehicle energizes it, and that coil is placed where the manufacturer expects you to hold a dead fob. On many Toyota and Lexus models you touch the fob to the START button, on many Honda models you hold it flat against the button, and on several Nissan and Infiniti models you press the button with the fob itself. Other makes put the coil on the steering column or in the center console. Your owner manual lists the exact spot under the discharged key battery section.
Find the emergency key blade first. Nearly every smart fob hides one, released by a catch on the side or the back of the housing. Then find the keyhole: on most modern cars the driver door cylinder sits under a small cap or trim cover on the handle, which pops off with the blade or a trim tool. That is a free fix you can do in the parking lot. Call us when the blade is missing too, when the cylinder is seized, or when the door opens and the car still will not start.
Bring them all, and say so on the phone. On several older Honda and Toyota onboard relearn procedures the vehicle writes a fresh key list, and any key not present during that procedure stops working afterwards. That turns a spare in a drawer at home into a dead spare. It also changes the job description: adding a key while one still works is not the same job as all keys lost. Many Ford, Honda and Toyota models show the number of registered keys in the instrument cluster information menu, which is worth checking before we start.
Usually yes, when the fob is physically intact. If the hardware is fine and only the pairing was lost, the work is duplication and re-registration at $100 to $250, and no new fob has to be bought. A brand new fob is a different tier because the hardware itself is part of the cost: domestic transponder programming is $150 to $250, smart proximity programming is $250 to $500, and luxury European programming is $250 to $450. Programming carries a flat surcharge of fifty dollars between 9 PM and 7 AM local time, and on Sundays and federal holidays.
That is range loss, and it is a different failure from total silence. The usual causes are a cell that is weak but not flat, a corroded battery terminal, a cracked solder joint on the battery pad, a worn carbon pad under the button, or a damaged antenna trace on the circuit board. Two of those are cleanable and two are solderable, so a fob with range loss is often repairable. Environment matters too: if range collapses in one parking garage and returns at home, that is RF interference and there is nothing wrong with the fob.
Early 2000s vehicles like this one often use a blade key for the ignition and a completely separate remote for the alarm and the door locks, so the remote failing does not stop the car from starting and the alarm has no way to be disarmed from your hand. It is a different job from a modern push to start fob: the replacement remote is matched by the FCC ID printed on the old housing, then paired to the receiver. Work of this era is routine for us, and so are the work vans at the other end of the range, including Freightliner Sprinter and GMC Savana.

Once you know what broke, here is the job

Each automotive service has its own page with the process, the published price range, and what the van brings to you.

Car Lockout

Mobile car lockout 15-30 min, no damage

See service

Lost Car Key Replacement

Mobile cut and OEM programming on-site

See service

Car Key Programming

Transponder, smart key, proximity fob pairing

See service

Smart Key & Key Fob

Push-to-start, proximity fobs, 2014+ vehicles

See service

Ignition Repair

Cylinder replacement, Mercedes ESL, BMW EWS

See service

Broken Key Extraction

Snapped key removal without drilling

See service

Car Key Duplication

Spare keys, copies, transponder cloning

See service

Trunk Lockout

Mobile trunk opening 15-30 min

See service

ECU & Module Programming

ECU, BCM, PCM, TCM flashing and coding

See service

Luxury Key Programming

Mercedes, BMW, Range Rover, Audi, Porsche, Bentley

See service

Related Reading

Prices, credentials, and what to do when the car will not open at all.

Automotive Locksmith Prices

Automotive price list with day and night rates

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How to Verify a Locksmith in 60 Seconds

Three-step locksmith verification before you hire

Read guide

Locked Out at Night: What to Do

Emergency lockout safety guide

Read guide
Prefer Spanish? Read El control de mi carro no funciona.
24/7 Live Dispatch

Checked everything and it is still dead? Tell us what you saw.

Say which fob failed, whether the blade opened the door, and what the security light did. That is enough for us to quote the exact tier on the phone before a van leaves.

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