Peugeot 508 ECU Error Power Loss

I also drive a 508 (not the hybrid version) and I had similar symptoms a while back – reduced power and an ECU error. It turned out to be a faulty relay. The main relay, as you suspect, could very well be the culprit. Have you checked the relay itself for any signs of damage or corrosion? Relays are electromechanical switches, often used in control systems. If they fail, they can cause all sorts of problems with vehicle electronics.

Thanks! That's very helpful. I haven't physically inspected the relay yet. Where is the main relay typically located in the 508? And when you say "relay," are you referring to the engine control unit relay?

Yes, I am referring to the engine control unit relay. In my case, the workshop confirmed that the main relay was defective. I'm not sure about the exact location in the hybrid version, but usually, it's in the engine compartment's fuse box or near the ECU. Given the error message and symptoms, a visit to a workshop might be unavoidable, so they can check the control system. It cost me about 120€.

Thank you very much for the information! I appreciate you sharing your experience. I will schedule an appointment with a trusted workshop to have the ECU and the relays inspected. It's reassuring to know that a defective relay is a plausible explanation and that the repair costs might not be exorbitant. I will post the solution.