Renault Master ECU Error

Greetings. I also drive a Renault Master with a diesel engine. The symptoms you describe are indeed suggestive of a malfunctioning ECU. Reduced power and stored error codes are typical indicators. Have you checked the wiring harness and connectors leading to the ECU for any signs of corrosion or damage? A visual inspection is always a good starting point. Also, can you provide the exact error code you retrieved from the diagnostic tool?

Thanks for the quick reply! I visually inspected the wiring harness and connectors, didn't notice anything obvious like corrosion. The error code is P0606 - Internal Control Module Processor. Does this ring any bells?

Affirmative. Error code P0606 strongly indicates an internal fault within the ECU itself. Given the symptoms and the error code, a defective main relay is a plausible explanation. Unfortunately, without specialized equipment, diagnosing and repairing ECU faults can be challenging. I would recommend consulting a qualified workshop with expertise in automotive electronics for a proper diagnosis and potential repair. They will be able to perform more in-depth testing and potentially reflash the ECU if necessary.

Thanks a lot for your help! I took it to a workshop, and you were spot on - it was the main relay. Replaced it for 120€ and now it runs like new.