1. Record exactly what happens
Write down the dashboard message, or take a photograph while the vehicle is safely parked. Note whether it appears when unlocking, pressing the start button or switching the vehicle off. These are different situations.
For example, Nissan’s LEAF handbook distinguishes a key outside the vehicle from a key the system cannot recognise. That is why “key not detected” should not automatically become a request for reprogramming.
- Does the remote unlock the doors?
- Does the dashboard respond when you attempt to start normally?
- Is there a separate low-key-battery warning?
- Did the problem follow a drop, water exposure or recent battery work?
2. Compare the key you normally use with your spare
Confirm you have the correct key for the vehicle. If a known working spare is available, note whether the same problem occurs with it. Keep the results simple: “the spare starts it” is more useful than guessing which component needs replacing.
If both keys behave the same way, report that too. It helps the technician decide what to investigate; it does not prove that both keys are faulty.
- Have all available keys ready for the assessment.
- Do not force a key, reader or start button.
- Mention whether the fault occurs everywhere or only in one location.
3. Find your model’s documented backup method
Some vehicles have a specific backup starting method for a depleted key battery. The reader position and procedure vary. Use the owner’s handbook for your exact model and year instead of following a sequence for a similar-looking car.
Nissan’s 2024 Juke manual has its own procedure for key-battery discharge or interference. It is an example of why instructions must stay with the vehicle they describe. If you cannot identify the correct procedure, ask for help before experimenting.
4. Send a useful enquiry
Give us the registration, make, model, year and postcode, followed by the warning and the results with each key. Include the relevant photographs and say whether the vehicle is accessible.
We can then discuss key assessment, programming or replacement for your vehicle. Ask which work is proposed and what the total covers before booking. A dashboard warning alone is not enough to choose a replacement part.
Common questions
Does “key not detected” mean I need a new key?
Not necessarily. The message needs to be considered alongside the vehicle’s behaviour, the key condition and the result with a spare. Arrange an assessment before ordering a replacement.
Can I use the same backup-start instructions for every car?
No. Reader positions and procedures differ. Use the handbook for the exact model and year, and ask for help if the instructions do not match your vehicle.
Sources and further reading
These sources support the general guidance. For vehicle operating instructions, use the handbook for your exact model and year.