One key failing is a key problem. Both keys failing on the same day is a vehicle problem, and the single most expensive mistake you can make right now is buying a third key. Call or text (817) 214-2934 before you order anything.
Quick Answer
As of September 2026, when every key stops working at once the cause is almost always in the vehicle, not in the keys — most commonly a weak or failing vehicle battery, a blown fuse, a failed receiver ring or antenna, or a body control module fault. Start with the battery, because it is free to check and it explains more of these calls than everything else combined. Repairs range from a $0 battery charge through a fuse, up to $100–$400 for immobilizer work and $150–$600 for module-level programming. A new key fixes none of it.
Why Two Keys Rarely Fail Together
Keys fail for reasons that are specific to that key: a dropped fob, a cracked chip, a worn blade, a flat coin cell. Those things happen one key at a time. The odds of two independent keys failing within hours of each other, by coincidence, are small.
What is not small is the chance that the one thing both keys depend on has failed. Both keys talk to the same antenna. Both are read by the same module. Both draw on the same vehicle battery for the system to work at all. When the shared part goes, every key goes with it — and from the driver's seat that looks identical to "my keys broke."
So the diagnostic question is not "which key is bad." It is "what do both of these keys have in common," and the answer is a short list you can work through in order.
Work the List in This Order
1. The vehicle battery. Always first.
A battery that still cranks the engine can still be too weak to run the security system properly. Low voltage produces exactly the symptoms people blame on keys: the dash lights up but nothing happens, the security light behaves oddly, the remote unlock works from two feet and not from ten, the vehicle starts on the third try and not the first.
Check it before anything else. If the headlights dim noticeably while cranking, if the vehicle sat for several weeks, if the battery is more than four years old, or if you jumped it recently and it has been strange since — that is your prime suspect. A charge or a replacement is the cheapest fix on this entire page and it costs you nothing to rule out.
This is also why "it will not start after a battery change" is its own category. Some vehicles need a relearn after the power is interrupted, which is a programming job rather than a key job, and on push-to-start platforms it is a recognised procedure rather than a fault — the same relearn described in our Chevy Silverado push-to-start BCM relearn write-up.
2. Both fob batteries.
Less of a coincidence than it sounds. Vehicles are frequently delivered with two fobs whose coin cells were made in the same batch, fitted on the same day, and used in the same climate. Hood County summers are hard on them. They can genuinely reach the end within weeks of each other.
The tell: the vehicle still starts when you hold the fob against the start button or the steering column, but the buttons do nothing from a distance. That is a dead transmitter with a live transponder, and it is a few dollars of battery rather than a key.
3. Fuses.
One blown fuse can take out keyless entry, the receiver circuit, or the module that reads the key, and it will do it to every key equally. Owner's manuals list the relevant fuses. It is a five-minute check and occasionally it is the whole answer.
4. The receiver ring or antenna.
On a turn-key vehicle there is a coil around the ignition lock that reads the chip in your key. On a push-to-start vehicle there are antennas distributed around the cabin. If that coil fails, comes unplugged, or is damaged, the vehicle stops being able to read any key.
This is the classic aftermath of work near the steering column — an ignition replacement, a stereo install, a dash repair, a stolen-vehicle recovery. If something was done to the vehicle in the days before every key stopped working, the connection between those two facts is rarely a coincidence.
5. The body control module or immobilizer module.
Higher on the price list, lower on the probability list, and genuinely does happen. Water intrusion is the most common trigger in this part of Texas — a module in a footwell or under a seat that has been wet is on borrowed time regardless of how it behaves today. We wrote about exactly that pattern in our Chevy Tahoe and GMC Yukon water-damaged fob and BCM guide, and it applies far beyond those two models.
The other module case is a corrupted immobilizer that has lost its key list — the vehicle is healthy but no longer recognises anything. That is a programming job, not a parts job, and it is what our immobilizer programming service exists for.
6. Aftermarket alarms and remote starters.
Anything wired into the ignition circuit can interrupt it when it fails. If the vehicle has an aftermarket remote start or alarm — common on trucks around here — it belongs on the suspect list well above the keys.
What Your Vehicle Is Telling You
The exact failure narrows the list considerably.
| What happens | Most likely cause | Typical Granbury cost to resolve |
|---|---|---|
| Nothing at all — no dash lights, no click | Vehicle battery or main connection | Charge or replace battery; no locksmith needed |
| Dash lights up, engine will not crank | Battery, starter circuit, or security lockout | Battery first; $100–$400 if immobilizer |
| Engine cranks but will not fire, security light on or flashing | Immobilizer is not accepting any key | $100–$400 immobilizer, $80–$350 key relearn |
| Remote buttons dead, but vehicle starts with key held to the column | Both fob batteries, or the receiver | A few dollars, or $80–$350 |
| Key will not turn in the ignition at all | Mechanical — worn cylinder or steering lock | $100–$350 ignition repair |
| Everything died right after a battery change or jump | Module needs a relearn | $80–$350 programming |
| Everything died right after work near the dash | Disturbed or unplugged antenna | Quoted on inspection |
Those cost bands are the ones published across this site, including on our ignition repair page and our auto locksmith services and costs guide. The diagnostic itself is what decides which line you are on, and it is worth doing before any money is spent on parts.
The Mistake That Costs the Most
Someone whose keys have both "failed" orders a replacement key online, waits three days, has it cut and programmed, and discovers the vehicle still will not start — because the vehicle could never read a key in the first place. Now they have paid for a key, paid for programming, and still have the original fault.
The reverse mistake is cheaper but still wasteful: paying for a diagnostic on a vehicle whose battery was flat all along.
Both are avoided by the same ten minutes. Check the battery, check the fuses, note exactly what the vehicle does when you try to start it, and describe that to whoever you call. A good locksmith will ask these questions before quoting, and the answer sometimes is "this is not a locksmith job, get the battery tested first." We say that several times a month and it is the right answer.
When It Genuinely Is the Keys
Two exceptions are worth naming, because they do exist.
Both keys lived together and were damaged together. Two fobs on one ring that went through a wash cycle, sat in a flooded footwell, or spent an afternoon in Lake Granbury are not independent any more. They shared an event. That is a genuine both-keys-failed case, and it is a key job.
The vehicle was reprogrammed and your keys were erased. If a module was replaced, or somebody ran an all-keys-lost relearn without your keys present, your keys are no longer on the list. They are physically fine and electronically strangers. That is a programming job in the $80–$350 band — the module has to be told to trust them again, or new keys have to be written. It is also the exact mechanism that makes an immobilizer relearn a real security tool, as covered in our Hyundai Santa Fe and Kia Sorento immobilizer module programming guide.
Push-to-Start Vehicles Behave Differently
On a proximity vehicle the failure modes shift, because there is no key going into a lock.
If neither fob is detected, try the manufacturer's backup position — most push-to-start vehicles let you hold the fob directly against the start button or a marked spot on the steering column, which reads the transponder even with a dead fob battery. If that starts the vehicle, you have two dead coin cells and nothing more serious.
If the backup position also fails, the vehicle is not reading any transponder and you are back on the shared-component list: battery, fuse, antenna, module. The mechanical blade hidden inside the fob will still open the door, which is worth knowing before you assume you are locked out as well as stranded. The differences between these systems, and what each one actually needs, are laid out in our comparison of transponder keys, smart keys and key fobs.
What We Need Before We Come Out
- Year, make, model, and trim
- Exactly what happens when you try to start it — no lights, lights but no crank, cranks but will not fire
- Whether the security or immobilizer light is on, off, or flashing
- Whether the remote buttons still work
- Whether anything was done to the vehicle recently — battery, jump start, stereo, ignition, body work
- Whether the vehicle has an aftermarket alarm or remote start
That last question changes the diagnosis more often than people expect, so it is worth answering honestly even if the install was years ago.
Proof of ownership is required on any job where keys are made or programmed — registration, title, or insurance in your name alongside photo ID. In Texas, locksmiths are licensed through the Department of Public Safety Private Security Program, and it is entirely reasonable to ask about that before anyone opens a door.
How the Visit Runs
We start with the diagnosis rather than with parts. Battery voltage and a load check, fuses, then a scan of the immobilizer and body modules for stored faults and for the list of keys the vehicle currently recognises.
That key list is the decisive piece of information, and it is why this needs a diagnostic tool rather than guesswork. If the vehicle says it knows two keys and simply cannot read them, the fault is in the reading — antenna, wiring, module. If it says it knows none, the keys have been erased and need to be rewritten. If it says it knows two and reads one of them fine, you never had a both-keys problem at all.
From there the job is whatever the diagnosis says it is: a relearn, an antenna, a module, an ignition, or a note telling you to have the battery replaced first. We quote before doing, and where the honest answer is "this is not a key problem," that is what you get told.
Frequently Asked Questions
Both my keys stopped working on the same day. Is that possible? It is possible but uncommon as a coincidence. Far more often the shared part failed — the vehicle battery, a fuse, the receiver ring, or the module that reads keys. Start with the battery. It explains more of these calls than every other cause put together.
Should I just buy a new key? Not yet, and this is the most expensive mistake available. If the vehicle cannot read any key, a third key will not start it either. Diagnose first; buy parts second.
Can a weak car battery stop my key from working? Yes, and it does so frequently. Low voltage disrupts the immobilizer and body modules before it stops the engine cranking, which produces intermittent no-starts, odd security-light behaviour, and shortened remote range. A battery that still cranks can still be the cause.
My fob does not unlock the doors but the car still starts. What is that? A dead fob battery, usually. The buttons are a radio transmitter that needs power; the transponder inside is passive and works without it, which is why holding the fob against the column or the start button still works. A coin cell fixes this.
What does it cost to fix an immobilizer that will not read any key? Immobilizer work in Granbury runs $100–$400, and module-level programming $150–$600, depending on the platform and what the scan finds. Key relearning on its own is $80–$350. The diagnostic determines which of those applies before any parts are ordered.
Everything stopped after I changed the battery. Did I break something? Almost certainly not. Some vehicles need a relearn after power is interrupted, and some aftermarket alarms lock out when voltage drops. It is a recognised procedure in the $80–$350 range rather than damage, and it is one of the more common calls we take.
Could water have caused this? Yes. A soaked fob, a wet footwell, or a module that has ever been under water are all real causes, and water damage often shows up days or weeks after the event rather than immediately. If the vehicle or the keys have been wet, say so — it changes where we look first.
Do you come out, or do I need it towed? We come to you. Diagnosing a no-start is exactly the job that should not require moving the vehicle, and we cover Granbury, Acton, DeCordova, Pecan Plantation, Tolar, Lipan, Cresson, Nemo, Bluff Dale, Glen Rose, and roughly 25 miles out.
Get It Diagnosed Before You Buy Parts
Tell us the year, make, model, and exactly what the vehicle does when you turn the key or press the button, and we will tell you whether this is a key job at all. Call or text (817) 214-2934, weekdays 8:00 AM to 7:00 PM, Saturdays 8:00 AM to 5:00 PM, with 24/7 emergency availability. You can also request service through our contact page or read how all-keys-lost programming runs on a push-to-start truck.
Sources
- Texas Department of Public Safety — Private Security Program
- National Automotive Service Task Force — Vehicle Security Professional Program
- National Highway Traffic Safety Administration — vehicle safety and recalls
- National Insurance Crime Bureau — vehicle theft resources
- Associated Locksmiths of America
- Texas Department of Motor Vehicles — vehicle registration and title