Mercedes-Benz CLK500 key won't turn after vehicle was running fine on Mercedes-Benz CLK500

Some Mercedes-Benz CLK500 owners report experiencing issues with their key not turning after the vehicle was running fine, which may be due to a faulty key that requires replacement, though this is not guaranteed to solve the problem. If replacing the key does not help, owners may encounter complications related to the steering wheel lock, the Electronic Ignition Switch (EIS), or the Electronic Steering Lock (ESL). In some cases, the EIS module might need replacement, or the key and smart key remote may require reprogramming to address the turning issue. Additionally, it is crucial to check the connection between the key and the vehicle, as a proper signal must be transmitted to the Electric Steering Column (ESC) control module to unlock the steering and allow the key to turn. It is also important to note that the remote key battery is not related to the key turning issue, as the engine can start without a battery in the ignition key, which is only necessary for central locking system operation. Addressing these potential causes step by step is advisable for effective diagnosis and resolution.