If you’re seeing fault code on a Renault Mégane 2 (typically 2002–2009), it points to a "Turbocharger pressure regulation circuit" issue (often described as boost pressure control solenoid valve malfunction).
Before replacing the turbo or chasing boost leaks, check the small black electro-valve (boost pressure solenoid) located near the battery/air filter housing. It fails frequently due to oil vapor contamination. Swap it with the identical EGR solenoid nearby (same part number) to test. If the fault moves, replace the valve (cost ~€30-50, not the turbo).