Error code occurred during ECU upgrade (5021-27-7F33)

Symptom:
ECU upgrade in progress, error code [5021-27-7F33]

Cause:
The controller has returned a 33 negative response to the ECU upgrade security command. This may be due to a failure in the security authentication process between the vehicle and the controller during the ECU upgrade.

Resolution:

1. Ensure the tablet is connected to Wi-Fi or LTE/5G

2. Log out and log in again to the diagnostic application and retry the upgrade.

3. Check whether the ECU upgrade was performed using automatic mode or manual mode.
   If manual mode was used, confirm that the upgrade was attempted under the appropriate category specific to the controller.

4. Ensure that the vehicle is NOT equipped with any aftermarket devices.

5. Ensure that no works or modifications have been performed on the gateway installed in the vehicle.

6. If the issue persists, please contact the controller manufacturer or a vehicle research institute for further assistance.

[Further Resources]

• What to Do When an ECU Upgrade Fails

• How to Send the Error Log Report on GDS Smart/KDS2.0

• How to Retrieve ECU Logs from Your Tablet on GDS Smart/KDS2.0