A key not detected warning shows in most cases because the coin cell in the key fob is flat, and holding the fob against the start button starts the car until a new battery is fitted.
Key not detected is the dashboard message of a keyless car that has searched the cabin for its smart key and received no valid reply. Antennas in the cabin send a short range request, the fob answers with a coded signal, and the car allows the start button to work only after the two match. The warning means that exchange failed, not that the key is gone. Five checks clear the common cases at the car, and seven causes explain the rest, four in the fob, one in the air and two in the car. Two cases stand apart, both keys failing together and a warning that follows an attempted theft, and each has its own section. A smart key is paired again at the car in 30 to 60 minutes.
A fix, driving on, a key inside the car, a start, a battery change, a Mercedes, a Ford, a Nissan, a Renault card, an intermittent warning, a phone, a signal blocking pouch, the car battery, theft and the time for pairing raise fifteen further questions.
The list below gives four key takeaways on a key not detected warning.
- A flat coin cell in the fob is the most common cause, and the car still reads the fob at the backup position.
- A phone, a charger or a second fob beside the key blocks the reply and brings the same message.
- Both keys failing on the same day place the fault in the car and not in either fob.
- An auto locksmith pairs a smart key again at the car, and deletes a stolen key from the memory in the same visit.
What clears a key not detected warning?
Five checks clear a key not detected warning in most cars, and the first one gets the engine running within a minute. The list below gives the five checks in order.
- Hold the fob at the backup position, on most cars flat against the start button, and press the button with the foot brake pressed.
- Move phones, chargers and other fobs away from the key, then press the start button again.
- Fit a new coin cell of the type printed on the old cell, usually a CR2032 or a CR2025, with the plus side facing the same way.
- Try the spare fob, since a spare that works places the fault in the first fob.
- Check the interior lights, and charge or jump start a car battery that leaves them dim.
The backup position is the start button on many cars, and the steering column or a marked slot on others. A key not detected warning that survives all five checks points to a damaged fob, a lost pairing or a fault in the car.
What does key not detected mean?
Key not detected means the car asked for its smart key and received no valid reply from inside the cabin. The wording changes with the make, and the table below gives six forms of the same message.
| Message on the dashboard | Where drivers report it |
|---|---|
| Key not detected | Mercedes, Peugeot, Volvo, Ford, Toyota |
| No key detected | Ford, Nissan |
| Key not in vehicle | Kia |
| Keyless remote not detected | Honda |
| Key ID incorrect | Nissan |
| Card not detected | Renault, Dacia |
The first four forms say that no fob answered. The fifth says that a fob answered with a code the car does not hold. Each form of the key not detected message blocks the start button and leaves the doors, the lights and the radio working.
Why does a car say key not detected?
A car says key not detected because the fob sent no reply, the reply was blocked or the car failed to read it. The list below gives seven causes in order of frequency.
- A flat coin cell leaves the fob too weak to answer the cabin antennas.
- A phone, a wireless charger, a laptop or a second fob beside the key blocks the reply.
- A weak car battery starves the receiver and the antennas of their 12 volts.
- A fob that was dropped or soaked has a cracked joint or corroded tracks on its circuit board.
- A lost pairing, often after the car battery was disconnected, leaves the car with no stored key.
- A signal blocking pouch or a metal tin around the fob stops the reply by design.
- A failed cabin antenna or receiver leaves the car unable to hear any fob.
The first, fourth, fifth and sixth causes sit in the fob, the second sits in the air and the third and seventh sit in the car. A key not detected warning that comes and goes points to the first two. Two cases follow a different path, and the next two sections cover them.
What if both keys are not detected?
Both keys are not detected where the fault sits in the car, and two fobs that fail on the same day rule out a flat coin cell.
Three faults stop every key at once. A weak car battery is the first, and dim interior lights confirm it. A lost pairing is the second. Some cars clear the stored keys after the 12 volt battery is disconnected, and every key then requires programming again before the start button works. A failed cabin antenna, receiver or body control module is the third, and it shows as a key not detected warning in every parking place with every fob. Two keys that fail in one place only point to interference at that place and not to the car.
Does attempted theft stop key detection?
An attempted theft does stop key detection in some cases, and a warning that first appears after a break in is treated as damage until a scan proves otherwise.
Thieves who reach the diagnostic port try to program a key of their own. A failed attempt leaves the stored keys erased or the system locked, and the car then shows key not detected with the correct fob in the cabin. Force on the door lock, the steering column or the dashboard trim tears the wiring to an antenna. A key that was taken, dropped or crushed during the attempt no longer answers at all. Drivers photograph the damage and report it to the police and the insurer before any repair, since the crime reference supports the claim. The existing keys are then paired again with diagnostic equipment, and any missing key is deleted from the memory of the car.
Who fixes a key not detected warning?
An auto locksmith fixes a key not detected warning where the fob or the pairing is at fault, and an auto electrician or a main dealer repairs a failed antenna, receiver or control unit.
The work happens at the car. The fob battery and the signal are tested first, the spare is tried and the fault codes are read through the diagnostic port. A smart key that lost its pairing is paired again, and a fob beyond repair is replaced and programmed in the same visit. ADC Locksmith Liverpool carries out smart key programming in Liverpool from £120 with no call out fee and no VAT, usually in 30 to 60 minutes, 24 hours a day. Craig Evans holds SERMI approval, the accreditation for access to the security data of the car maker, and checks photo ID and proof of ownership first. A scan that places the fault in the car is reported to the driver with the fault codes.
What does fixing key not detected cost?
Fixing key not detected costs £2 to £5 for a coin cell and £120 to £300 for a smart key programmed to the car, with three jobs in between. The table below compares five fixes by price.
| Fix | Price | Who does it |
|---|---|---|
| New coin cell fitted at home | £2 to £5 | The driver |
| Fob battery replaced and tested at the car | From £25 | ADC Locksmith Liverpool |
| Remote or key synchronised again | From £60 | ADC Locksmith Liverpool |
| Keys programmed again after a battery disconnect | £60 to £120 | ADC Locksmith Liverpool |
| Smart key supplied and programmed | £120 to £300 | ADC Locksmith Liverpool |
Most key not detected warnings end at the first row. ADC Locksmith Liverpool gives a fixed price on the call, before travel.
How do drivers prevent the warning?
Five habits prevent the warning, and a coin cell changed every two to three years removes the most common cause. The list below gives the five habits against a key not detected message.
- Change the fob coin cell every two to three years, or at the first low battery message.
- Carry the fob in a pocket of its own, away from the phone.
- Keep the spare fob working with a press once a month.
- Hold the car battery healthy with a regular run or a trickle charger.
- Take the fob out of its signal blocking pouch before the start button is pressed.
A fob that asks for a second press of the start button is giving the early warning. A new cell at that stage costs less than any call out.
What else do drivers ask about key detection?
Drivers ask about key detection in fifteen further questions on a key not detected warning. A fix, driving on, a key inside the car, a start, a battery change, a Mercedes, a Ford, a Nissan, a Renault card, an intermittent warning, a phone, a signal blocking pouch, the car battery, theft and the time for pairing are the fifteen topics, and the questions below answer each one.
Frequently asked questions
How do drivers fix key not detected?
Drivers fix key not detected in most cases with a new coin cell in the key fob.
The fob held against the start button gets the car going in the meantime.
Does a car still drive with no key detected?
Yes, a car still drives with no key detected once the engine is running, and the warning never stops the engine.
The guide to how a keyless car drives without the key covers the restart.
Why does the car say no key detected with the key inside?
The car says no key detected with the key inside because the fob is too weak to answer the cabin antennas.
A phone or a second fob beside the key blocks the reply in the same way.
How does a car start with no key detected?
A car starts with no key detected when the fob is held at the backup position, most often the start button.
Each make has its own spot to start a keyless car on a dead fob.
Why is the key not detected after a battery change?
The key is not detected after a battery change where the cell is the wrong type, sits upside down or the pairing was lost.
The guide to a key fob not working after a new battery lists five reasons.
What does key not detected mean on a Mercedes?
Key not detected on a Mercedes means the car senses no key in the cabin, and a flat fob battery is the usual cause.
A new coin cell clears the message in most cases.
What does key not detected mean on a Ford?
Key not detected on a Ford means the keyless fob gave no reply to the car.
The fob battery, the car battery or interference causes it. The Ford key not detected message guide shows the backup position.
What does Key ID incorrect mean on a Nissan?
Key ID incorrect on a Nissan means the car received a code that matches no stored key.
The guide to the Nissan red car with key light gives the fixes.
What does Card not detected mean on a Renault?
Card not detected on a Renault means the car has not read the hands free card.
A flat card battery, electronic equipment near the card or a worn card is the usual cause.
Why does the warning come and go?
A weak fob cell makes the warning come and go, since the reply drops out now and then.
A warning that shows in one car park only points to interference there.
Does a phone block the key signal?
Yes, a phone blocks the key signal where it rests against the fob in the same pocket.
Wireless chargers and a second fob have the same effect.
Does a signal blocking pouch cause key not detected?
Yes, a signal blocking pouch causes key not detected, since the pouch stops the fob answering the car.
The fob comes out of the pouch before the start button is pressed.
Does a weak car battery cause key not detected?
Yes, a weak car battery causes key not detected, since the receiver and the antennas run on its 12 volts.
Dim interior lights confirm it, and a charge clears the message.
Is a key not detected warning a sign of theft?
No, a key not detected warning is not a sign of theft in most cases, since a flat fob cell explains it.
A warning that follows a break in or damage near the diagnostic port is the exception.
How long does pairing a smart key take?
Pairing a smart key takes 30 to 60 minutes at the car with diagnostic equipment.
A lost or stolen key is removed from the memory of the car on request in the same visit.
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