Seat Tarraco Diesel ECU Problem Resolved

That's a tricky situation. Intermittent ECU problems can be a real headache. Have you checked the basics, like battery voltage and ground connections? A weak battery or poor grounding can sometimes cause spurious errors with vehicle electronics and affect the computer module. Before condemning the ECU, it is better to make sure the power supply is consistent. Have you tried a system reset of the ECU to see if the error clears? What specific error codes are stored in the error memory?

Thank you for the response. Yes, the battery voltage and ground connections appear to be in order. I did attempt a system reset, but the error persists, and the reduced engine performance is still evident. The error code logged indicates a malfunction within the Engine Control Unit itself. Could a defective main relay genuinely be the culprit, and if so, how can I confirm this without replacing the ECU outright?

Given that you've already checked the basics and performed a system reset without success, and considering the error specifically points to an internal ECU fault, a defective main relay is indeed a strong possibility. While it is difficult to confirm without specialized equipment, corrosion or damage on the relay itself, are good indicators. It is rare but not impossible, I’d advise you to visit a competent workshop to ensure that no consequential damage on your ECU is present.

Excellent news I appreciate your guidance on this matter. As suspected, the main relay exhibited signs of failure, causing the ECU problems and reduced engine performance. Replacing it rectified the issue. The system reset also helped. The total repair cost was approximately 120€, a worthwhile expense to restore optimal engine performance.