Error Code During ECU Upgrade (1000-C8-0027)

Symptom:  Error code [1000-C8-0027] occurs during an ECU upgrade.

Cause: Socket connection failure during Ethernet event security authentication.

Solution: 

1. Check whether any aftermarket equipment is installed in the vehicle.
2. Verify that the ECI cable is properly connected and confirm the tablet's static IP address.
3. Verify the diagnostic tool connection and confirm that the gateway control unit's sensor output is displayed correctly.
4. Disconnect the vehicle power connector, wait 5 minutes, reconnect it, and then retry the ECU upgrade.