I have a 2007 Ford Focus 1.8tdci. Last week I got an intermittent message displayed on the dashboard saying 'Steering Assist Failure'. I didn't see it for a couple of days but then, at the beginning of the week, it came on again and hasn't gone off since.
I've topped up the power steering fluid and had the power steering pump checked by a mechanic and he said he can't see any problems. He also plugged it into a computer but couldn't get an error code because the engine management light wasn't on.
When I'm driving it under 20mph the steering feels heavier than usual. Above 20mph the steering feels lighter than usual. The mechanic said it's probably a fault with one of the sensors controlling how much power steering to give relating to your speed.
Has anyone had or heard of a problem like this and how should I go about resolving it?
Thanks in advance.