This article explains how to resolve Error code 4001 that appears when you log in or try to use ECU Upgrade / S/W Management on the diagnostic tool (for example, KDS 2.0 / KDS 2.0). In most cases, the issue is related to a missing or outdated security certificate required for secure vehicle communication.
Quick links
Applies to
- Diagnostic tool: KDS 2.0 / GENESIS Smart / KDS 2.0
- Features: Login, ECU Upgrade, S/W Management
- Network: Wi-Fi / Hotspot
Symptom
You encounter Error code 4001 when logging in or when accessing ECU Upgrade or S/W Management.
Cause
This error can occur when the diagnostic tool does not have the required security certificate, or the certificate is not current. The certificate is needed for secure vehicle communication.
Resolution
Step 1) Trigger the background download of the security certificate
- Log out and quit/close the diagnostic app completely.
- Remove app cache and data: Troubleshooting: Error message "4001"
- Restart the diagnostic tool.
- Connect to a stable Wi-Fi network.
- Log in again.
- Wait a few minutes, then try ECU Upgrade or S/W Management again.
Note: The security certificate downloads in the background, any download progress on screen.
Step 2) Try a different network (hotspot)
If the same issue occurs after Step 1, connect to an unsecured network such as a mobile hotspot, then log in again and retry the feature.
Step 3) Remove aftermarket devices (if installed)
If an aftermarket device (for example, a black box) is installed in the vehicle, remove it temporarily and retry S/W Management.
Step 4) Reset vehicle power (battery negative terminal)
Disconnect the vehicle battery negative terminal for more than 10 minutes, then reconnect and retry.
If it still doesn’t work
- Confirm the diagnostic tool is connected to Wi-Fi/hotspot with internet access.
- Retry after waiting 3–5 minutes after login (to allow background certificate download).
- If possible, test on another network environment.
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