DS5 Air Valve Issue

An air valve issue on a DS5? Interesting. Why air valve right off the bat? Did you hook it up to a reader and get a specific code pointing to that system? Are you SURE about those vacuum lines? Sometimes cracks can be sneaky, especially with age and heat cycles. Could also be a sticky valve.

Good questions. No specific code screaming 'air valve'. I'm basing it on past experiences and research specific to this engine. Reader gave me generic 'lean' codes and I've systematically ruled out the usual suspects – fuel injectors, MAF sensor, etc. Regarding the vacuum lines – short of replacing every single one, is there a foolproof way to test them? Spraying carb cleaner around them while the engine's running didn't reveal anything obvious.

Okay, lean codes after ruling out the usual suspects... that does point towards a possible air leak somewhere. You're right, those vacuum lines CAN be a pain to diagnose without proper equipment. Based on what you've said, it still SEEMS like you're in the right ballpark. If you're not finding the leak yourself, it may be worth going to a workshop with proper smoke testing equipment. They can pinpoint the exact location much faster.

I appreciate the input. It ended up being exactly what I suspected: a cracked hose connection. I replaced the defective hose. Total cost: 175€, including the part and labor. I cleared the code, and the light's off... for now. Thanks again.