Buy YOUCANIC Pro Scanner
https://www.youcanic.com/scanner/

Get Factory Service Repair Manuals & Specs
https://www.youcanic.com/manuals

Ask Car Questions & Get Help
https://www.youcanic.com/forum/ If your MercedesBenz is displaying a "key not detected" message, it means that the vehicle's ignition system is unable to communicate with the key fob. This can be frustrating, but there are several potential causes and corresponding solutions to consider. Here are some steps you can take to troubleshoot and possibly resolve the issue:

1. **Check the Key Fob Battery**: The most common cause for this message is a depleted battery in the key fob. Replace the battery in the key fob with a new one and try again.

2. **Check for Interference**: Electronic devices or metal objects can interfere with the signal between the key fob and the vehicle. Make sure there are no other electronic devices nearby when trying to start the vehicle.

3. **Try the Secondary Key**: If you have a spare key, try using it. If the spare key works, then the problem is likely with your primary key fob.

4. **Reset the Key**: Insert the key into the ignition and turn it to the first position (do not start the engine). Then, remove the key and try to start the vehicle using the pushbutton start (if equipped). This can sometimes reset the key's communication with the vehicle.

5. **Check the Car's Battery**: If the car's battery is weak or dying, it may not have enough power to detect the key. Ensure that your car's battery is in good condition.

6. **Start Manually with Key**: Some MercedesBenz models have a backup way to start the vehicle using the key fob itself. Consult your owner's manual to see if this is an option for your specific model.

7. **Inspect the Electronic Ignition Switch (EIS)**: The Electronic Ignition Switch (EIS) in some MercedesBenz models can fail over time. If this component fails, it may not detect the key. You might need to consult with a mechanic or MercedesBenz technician for a diagnosis.

8. **Software Update**: Occasionally, a software update may be required for the vehicle's computer systems to improve key detection.

9. **Consult with a Dealership or Specialist**: If none of the above solutions work, it might be best to consult with a MercedesBenz dealership or a specialist. They will have specific diagnostic tools and expertise to identify the root of the problem and offer a solution.

In any case, while "key not detected" can be a common issue, it's essential to address it promptly to ensure the reliability and functionality of your vehicle.