Renault Modus ECU Error

ECU issues can be tricky. Before condemning the unit, have you checked the power supply and ground connections to the ECU? A faulty connection can mimic a failed ECU. Also, what specific error code are you getting? Knowing the exact code will help narrow down the possibilities.

Thanks for the response. I've visually inspected the power supply and ground connections, but I haven't done a thorough continuity test. I'll get the specific error code from the diagnostic report later today. Would a faulty connection always trigger a specific error code, or could it just seem like a generic ECU failure?

A bad connection could throw all sorts of weird codes, or none at all. It's unpredictable. While a relay could be the issue, ECUs themselves can fail. Given the symptoms and the age of the vehicle, it really needs a proper diagnosis by someone with experience in automotive electronics. It might be a simple fix, or it might need a new or refurbished ECU. Either way, I'd suggest a workshop visit.

The local workshop confirmed that the main relay was defective. Replacing it cost 120€, and the issue seems resolved. Thanks for pointing me in the right direction and confirming the potential root cause. I hope this helps other Renault Modus owners with similar ECU problems.