Peugeot 301 Check Engine Light

Air valve, huh? Could be a lot of things triggering that light. Engine stalling? Idle problems? Any other weirdness going on? Have you checked your air intake for blockages or leaks? Could also be a bad sensor messing with the air supply.

No stalling or idle problems. Just the light. You think it's definitely the air intake?

Well, 'definitely' is a strong word. But a defective hose connection from the pump to the valve seems likely given the symptoms you described. I'd suggest a workshop visit. Mine cost me 175€ to fix the same thing.

Thanks. Took it to the shop; hose connection was the issue. Replaced it. Light's gone.