Suggest to diagnose at workshop, usual keypoints of diagnose are:
1. Check the external wiring to exclude external wiring faulty possibility. May diagnose the ECU after confirmed the external wiring is fine.
2. Check if the exterior of the ECU has any sign of damage, is it secure in place tightly, soldering seal is it reliable.
3. Check the connection of wiring harness, especially the power supply and grounding cable.
4. Identify and confirm the ECU model used.