Error code occurred during ECU upgrade (5021-81-7000)

Symptoms

ECU installation issue: Incorrect physical installation may cause unstable communication.
ECU condition issue: The ECU may be in an unstable state, preventing proper communication.

Check physical installation – Ensure the ECU is properly installed.
Restart the ECU – Turn off the power to the ECU and restart it before retrying the upgrade.
IBU-BCM power reset – If the issue is related to the BCM, turn off the power and retry after 2 hours.

This error means the vehicle’s ECU (Electronic Control Unit) cannot communicate properly, causing the upgrade to fail.

If the problem continues even after following the basic troubleshooting steps (retrying, checking battery condition, etc.), please contact your NSC (National Distributor) for support.
If needed, we can provide a special file set with extended ECU response time to help retry the upgrade.
However, depending on the condition of the ECU, the upgrade may still fail even with the extended file.
If you've already tried reinstalling or reconnecting the ECU hardware and the issue remains, replacement or additional support from the vehicle manufacturer may be required, based on the automotive quality department’s guidance.