A flickering check engine light with a rough idle usually means an active misfire or unstable combustion—not just a loose sensor. Read the codes first and avoid hard driving until it’s checked.
What the flicker is telling you
On a Peugeot 308 III, a flickering check engine light is different from a steady one. A steady light says the ECU has logged a fault; a flicker often means a misfire is happening right now, cylinder by cylinder. Combined with rough idle, I’d suspect ignition, fuel delivery, or an unmetered air leak before I’d blame the light itself. On petrol models—especially the 1.2 PureTech—plugs, coils, and injectors are common suspects; on BlueHDi diesels, injector correction, EGR, and fuel pressure faults deserve a close look.
