E43.00 fault in inovance IS580 drive indicates "Speed sensor fault during motor auto tuning". This means the motor auto-tuning process fails due to incorrect or missing feedback from the speed sensor (such as an encoder or resolver) while the drive is trying to identify motor parameters.

• Ensure encoder/resolver is securely connected and no pins are bent or broken.
• Set the correct feedback device in drive parameters (e.g., resolver or incremental encoder).
• Check all entered motor data (voltage, current, poles, base frequency, etc.) match the motor nameplate.
• Disconnect the motor from the load and ensure it rotates without obstruction.