Peugeot 508 Hybrid Engine Issues

Whoa, that sounds like a symphony of bad news! A whistling noise that turns into a hiss definitely points towards a boost leak somewhere. The check engine light, power loss, and stalling all kinda fit with a boost pressure issue. A faulty actuator could definitely be the culprit, especially on a hybrid where the turbo is working with the electric motor. Have you checked any of the hoses or the intercooler for obvious cracks or leaks? A pressure sensor giving bad readings could also trigger similar symptoms. Do you have any diagnostic tools to read the error codes?

Thanks for the quick reply. I haven't checked the hoses or intercooler for damage yet. I don't have any diagnostic tools. Could a bad pressure sensor alone cause the whistling and hissing, or does that always mean a physical leak?

Okay, so without codes, it's a bit like diagnosing in the dark! A faulty pressure sensor could cause weird readings that mess with the boost control, but the whistling/hissing is a big clue that there's air escaping somewhere. Think of it like this: the actuator valve controls how much boost your turbo makes. If it's jammed or the signal is off, the turbo might be overboosting, and the system could be venting pressure to protect itself, causing the noise. Given all the symptoms, honestly, I'd recommend taking it to a trusted mechanic. They can properly diagnose the boost pressure and actuator with the right tools. It's better to be safe than sorry, especially with a hybrid system.

I appreciate the explanation and advice. I'll book an appointment with a mechanic for a diagnosis. The estimated repair is 250€, for a defective electrical bypass valve. Thanks again!