المبرد البيني أو خرطومه مسرّب

The charge air cooler or one of its hoses leaking, so pressurised air escapes before reaching the engine. The cooler is a pressure vessel in the boost circuit, mounted at the front where it takes stone impact, and its end tanks and their seams are where it splits.

The module sees boost falling short of target and blames what it commands — the wastegate, the vane actuator, the turbocharger — which is why a leak so often ends with an expensive part replaced and the fault unchanged. Two boost readings that disagree locate the leak between them.

A leak that only opens under boost is silent at idle, so it survives every inspection on a stationary engine. Pressure-test the charge system cold, which finds both a split cooler and a hose that will not hold. Oil pooling in the cooler is worth noting while it is off — it softens the hoses and lubricates the joints, so it both causes the release and points at turbocharger seal wear upstream.