What to Watch Out For
Starting and running problems and the car reverting to limp home mode can be due to the Power Control Module cluster gateway not closing properly and draining the battery overnight. May need to be reloaded with manufacturer data to overcome a sofware error.
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.
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.
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I think you would have a case if the above information is correct. Surely Ford know about this issue and the garage should have known what was the probable cause. Although (after an admittedly very quick google) i couldn't find a recall for the issue.