Peugeot 2008 Fault Memory Lock Active

That 'fault memory lock active' can be tricky. Is the car running normally otherwise? Any issues with starting, lights dimming, or other electrical components acting strangely? It's definitely pointing towards an ECU fault, possibly triggered by a voltage drop like you suspect. But it could also be a software glitch. Has the ECU been reflashed recently, or has any work been done on the car's electronics?

It seems to drive okay, but the lights flicker slightly at idle. No recent ECU reflashes that I know of. Is it something I should address promptly, or is it safe to drive for a short period?

Flickering lights at idle definitely strengthens the undervoltage theory. The 'fault memory lock active' message prevents clearing error codes and observing if they reappear, which complicates diagnostics. While it might run for a while, persistent undervoltage can damage the ECU or other components over time. It's better to get it checked. With that mileage, get the battery and alternator properly tested, but I still think it's worth going to the workshop.

Thanks for the detailed info. I appreciate it. I'll book it in with a workshop. Turns out that there was a short circuit causing the undervoltage. All fixed, though it set me back 240€.