The PCV valve may malfunction, and the baffles in the valve cover may become obstructed, allowing excessive oil to enter the air intake system as an additional potential cause. This may occur when fragments of a wet belt induce a failure mode, albeit it is not the sole cause of failure. This would be a more economical component to inspect or replace, and the aforementioned test would not detect this issue.
The PCV valve is typically integrated into the valve cover and may be serviceable; one can either clean the baffles or replace the entire valve cover, which includes the valve.
Examine the intake at the MAP sensor for excessive oil, or trace the smaller pipe (about 17-19mm ID) that connects the valve cover to the air intake and inspect the source.
The PCV system manages blow-by gases in the engine, and while all engines possess a mechanism for this management, it is particularly crucial in turbocharged engines, which generate greater blow-by compared to natively aspirated engines. The mechanisms employed for regulation include Positive Crankcase Ventilation (PCV), Closed Crankcase Ventilation (CCV), and Open Crankcase Ventilation (OCV), the latter of which is virtually obsolete under emission regulations, thus applicable only to vehicles manufactured prior to the 1970s or utilised in racing or off-road contexts where emission standards are not enforced.
PCV and CCV appear to be identical systems; however, the primary distinction in CCV is that the ECU must consider all the air. Your vehicle is equipped with a PCV control system, but only Peugeot diesel models utilise a CCV control system. The majority of diesel engines utilise CCV; however, certain models, such as Cummins, employ PCV control. On these engines, it is possible to install BOVs on the turbo without causing the ECU to malfunction, including stalling the engine due to unmonitored air. While BOVs are not essential for diesel engines, some enthusiasts appreciate the sound they produce.