Engine malfunction message on Ford Focus - what's the fault?

The engine malfunction message has come up on my 2008 Ford Focus 1.8 TDCI. There are no warning codes or lamps, so my mechanic has nothing to work with after plugging it in to the diagnostic scanner. Yet the message continues to come up, forcing the car into limp home mode. Any idea what could be wrong?

Asked on 24 August 2013 by ilovemycar

Answered by Honest John
Might need a new air filter. Simple, but often overlooked.
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Much improved 2004 Focus. Great to drive. Comfortable and well laid-out interior. Wide range of engines. Low emission ECOnetic versions offer 55mpg +.