Error Code Occurs During ECU Upgrade (5021-10-7005)

Symptom:  Error code [5021-10-7005] occurs during an ECU upgrade.

Cause:  A CAN bus fault occurred in response to the ECU upgrade communication open command.

Resolution: 

1. Check whether any aftermarket equipment is installed in the vehicle.
2. Check the diagnostic tool connection and confirm that the sensor output for the target control unit is displayed correctly.
3. If the connection and sensor output are normal, retry the ECU upgrade.