Nissan Dayz Air Valve Hose Issue

Sounds like a vacuum leak. Like a pinhole in a water pipe causing pressure drop, vacuum leaks mess with the air-fuel mix. Is it idling rough? If you have an OBD2 scanner, check the error code. Have you looked at the hoses for cracks or disconnections?

Thanks, yes, it is idling rough. I'm thinking about getting an OBD2 scanner. Where on the vacuum hoses should I look closely? Any common weak spots to watch out for?

Rough idle plus the light definitely points to a vacuum leak. Focus on hoses near the air intake and valve. Check connections to the intake manifold too. Since it's an older car, those hoses get brittle from age and heat, causing leaks. If you find a crack, a pro might be needed, could be more going on.

Good news: It was a cracked hose on the air valve, just like you said. The local shop replaced it. Cost me 175€. The check engine light is off, and it runs smoothly now.