Cause - Comes when internal communications failure/error or faulty control card of drive or due to faulty control card and power card or incorrect parameters. This fault typically occurs when there is a communication error between the various internal components of the drive.

1. If the error still occurs, replace the inverter.

2. Check control card using multimeter.

Other solutions :

1. Power cycle the drive: Turn off the power to the drive and wait for a few moments before turning it back on. This can sometimes resolve temporary communication issues.

2. Check the communication cables: Ensure that all communication cables, such as the RS485 or Profibus cables, are securely connected and free from any damage. If possible, try replacing the cables to eliminate the possibility of a faulty cable causing the communication fault.

3. Check the communication settings: Verify that the communication settings, such as baud rate and protocol, are correctly configured in the drive and match the settings of the connected devices or control system.

4. Update firmware: Check if there are any firmware updates available for the Micromaster 420 drive. Updating the firmware to the latest version can address known communication issues and improve the overall performance of the drive.

5. Reset parameters: If the fault persists, you can try resetting the drive to its default factory settings. This will reset all parameters and configuration settings, which may help clear any internal communication issues.