Might be this: Mysterious 'Engine System Faults' on diesel leading them to lose power and revert to limp home mode may be caused by an intercooler pipe weld fault leading to a crack in the pipe. On 1.6TDCI the thin steel turbo to intercooler pipe can split. It cracks in two places in opposite directions emanating from the "start" and "stop" of the upper bracket weld. Fractures are of a fatigue nature resulting from vibration, the bracket being rigidly attached to the engine. By May 2010, turbo failures were becoming increasingly common on high mileage 1.6TDCIs.

Problem of 1.6 and 2.0 16v diesels slipping into limp home mode put down to throttle butterflies sticking or their spindles wearing prematurely causing them to stick. The throttle position sensor identifies this and sends a message to the ECU to limit the engine to limp home mode.