Seat Cordoba Check Engine Light Air Valve Issue

Sounds like a vacuum leak. I had similar issues with my Cordoba. Check your vacuum hoses, especially those connected to the air intake manifold. Could be a simple crack causing a loss of manifold pressure.

Air intake manifold? Vacuum hoses? Could you be more specific?

Yes, that's it. The vacuum hoses are part of the air intake system; they regulate pressure. A leak there can throw off the whole system and trigger the check engine light. If you are not able to locate it yourself, I would suggest a visit to the workshop. They should be able to find the leak.

Confirmed. The hose connection from the pump to the valve was indeed defective. Repair cost 175€. Thanks for the advice.