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Mercedes-Benz Intermittent Ignition Problem


  • The Mercedes-Benz key works intermittently. The key works properly when it is warm. When it is cold, or the temperature drops below 20 degrees Celsius, it stops working.
  • The key doesn’t start the car when it is cold.
  • The key and ignition work properly all day when it is warm.

Possible Cause

  • These symptoms are often caused by weak joints in the EIS (Electronic Ignition System). Sometimes, these problems can be due to a defective SAM (Signal acquisition module).


If you are experiencing any problems described here, you must identify whether the problem is the EIS or SAM module. You will need a diagnostic scanner such as YOUCANIC Scanner to diagnose such problems properly.

Once you identify the defective module, you can get it repaired. You can find services to repair your old EIS and SAM module online.

Turn igniton off and waitNote that your original EIS module can be repaired and reinstalled without reprogramming. You can’t install a used EIS module in your Mercedes-Benz even if the unit has the same part number. EIS modules are locked to the vehicle, and the unit’s VIN must match the car. Your other option would be to get a new EIS or SAM module from the dealer and have them perform the programming.

Related fault codes

  • B1000 – Control Unit N73 EIS / EZS Control Unit is defective.

What is the Best Scanner for Diagnosing Mercedes-Benz Vehicles?

If you’re experiencing problems with your Mercedes-Benz, the YOUCANIC full system diagnostic scanner can provide invaluable assistance in troubleshooting the issues. By connecting to your car’s onboard computer, the scanner can read fault codes and provide detailed information about any problems with your engine, transmission, brakes, and other systems. Additionally, the scanner can perform diagnostic tests on various systems, such as the ABS, airbag, and steering systems, to help identify the underlying cause of any issues.

In addition to providing diagnostic information, the YOUCANIC scanner can save you time and money on repairs by enabling you to perform simple fixes yourself. For example, if you notice the check engine light on, the scanner can assist you in identifying the problem and determining if it’s a simple issue you can address at home or if you need to take it to a mechanic. This can help you avoid unnecessary trips to the repair shop, saving you both time and money.

Overall, the YOUCANIC full system diagnostic scanner is a powerful tool to help you maintain and troubleshoot your Mercedes-Benz. It’s an excellent investment for both DIY mechanics and professional technicians, as it can assist in diagnosing and resolving even the most complex automotive problems easily, saving you time and money on costly repairs.

One comment

  1. I have an issue with my keyless ignition. Most of the time it works fine. But sometimes it says not detecting the key. I’ve had the battery changed in the key so I know it’s not that.

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