The ‘Key Not Detected’ warning in Mercedes-Benz vehicles is a common issue related to the vehicle’s keyless entry and start system (KEYLESS-GO). This system allows the driver to unlock and start the car without physically inserting the key. When the system fails to detect the key, the instrument cluster displays ‘Key Not Detected,’ preventing engine start or locking/unlocking. This article explains how the system works, common causes of this error, diagnosis steps, and repair solutions.
What is the KEYLESS-GO System?
KEYLESS-GO uses a wireless transponder built into the key fob to communicate with antennas and sensors in the vehicle. When the key is within range, the system allows the driver to unlock doors, start the engine, or open the trunk without inserting the key. If the communication between the key and the vehicle is interrupted, the system will not detect the key.
Common Error Messages in the Instrument Cluster
When this issue occurs, common messages include:
• Key Not Detected
• Place Key in Marked Area (sometimes shown)
• Key Battery Low
Causes of Key Not Detected Warning
The most common causes of this warning are:
1. Weak or dead key fob battery.
2. Faulty key fob transponder or damaged key.
3. Interference from other electronic devices or signals.
4. Faulty keyless entry antennas in the vehicle (door handles, interior, trunk).
5. Wiring or connector issues between antennas and ECU.
6. Faulty Keyless-GO control unit (ECU).
7. Vehicle battery voltage problems affecting system communication.
How to Diagnose Key Not Detected Errors
Diagnosis begins with checking the key fob battery and replacing it if weak. If the issue persists, try using a spare key to rule out a defective key fob. Next, perform a diagnostic scan using Mercedes-Benz software such as Xentry, Vediamo, DTS Monaco, or the MBCOD Box with ELM327 to check for stored fault codes related to the Keyless-GO system. Inspection of vehicle antennas, wiring, and ECU is also necessary.
How to Fix Key Not Detected Errors
Steps to resolve this issue include:
1. Replace the key fob battery with a new CR2025/CR2032 battery.
2. Test with a spare key to confirm if the issue is with the key fob or the vehicle.
3. Inspect and replace faulty antennas (door handle antennas, interior antennas).
4. Repair or replace damaged wiring/connectors between antennas and ECU.
5. Replace or reprogram the Keyless-GO ECU if necessary.
6. In case of signal interference, move away from high-interference areas (e.g., near strong radio signals).
Preventive Maintenance for Keyless-GO
To prevent ‘Key Not Detected’ warnings, always replace the key fob battery at regular intervals, avoid exposing the key to water or strong impacts, and keep a spare key available. Regular system diagnostics and software updates from Mercedes-Benz service centers also help maintain functionality.
When to Contact a Specialist
If the warning persists after replacing the key battery and trying a spare key, professional diagnostics are required. At MBCOD in Dubai, we specialize in Keyless-GO system repairs, ECU programming, and antenna replacements. We also provide mobile diagnostics and emergency key programming across Dubai, Abu Dhabi, Sharjah, and Ajman.
Conclusion
The ‘Key Not Detected’ warning can be frustrating, but it usually relates to a simple issue such as a weak key fob battery. In more complex cases, it may involve antennas, wiring, or the Keyless-GO ECU. With proper diagnostics and repairs, the system can be restored to full operation. Trust MBCOD in Dubai and across the UAE for expert Mercedes-Benz Keyless-GO diagnostics and repairs.