Hello all.  New to the forum so I hope this has been posted correctly.

I have a Mk 2 2005 Focus Estate 1.6 Auto Ghia.  A few weeks ago the ABS warning light came on whilst driving.  It was intermitent for a few days but eventually remained on all the time.

I took it to National Tyres who plugged it in and told me I had a fault on both front sensors and the near side rear sensor.

I have had the car since 2008 and put 55000 miles on the clock.  In that time Ihave replaced both front wheel bearings and the rear near side one.  (Not sure if this coincidence or not) These have been done by a family friend who is an excellent mechanic.  

I purchased three new sensors and my mechanic went about changing them. When he replaced the front nearside sensor he noticed that the excitor ring was in 3 pieces.  As these come as part of a hub / bearing kit I purchased a new hub and this was fitted along with a new sensor.

The front offside hub looked okay so only the sensor was replaced.  The rear nearside hub is a sealed unit and less than 2 years old only the sensor was replaced.

Having completed the work the ABS light came on as normal and then went out after a few seconds.  However at 20 mph it came back on.  Switching the engine off and turning back on again the ABS light remains on.  At approximately 10-15mph it goes out however as soon as I brake the ABS kicks in.  At approx 20mph ABS light comes on and the brakes work normally.  

Light then stays on until I turn I turn off the engine and it repeats the above cycle.

Do I need the faults completely cleared? 

I'm thinking of changing the offside bearing to see if that helps as it seems to me that the new sensor is picking up that a wheel is not moving (incorrectly) when others are. As it is a new sensor and as I had issues with a similar aged hub in the nearside I was thinking that there maybe a similar fault with that hub/excitor ring after all.

Has anyone had similar issues or any other ideas?

Apologies for the long post but it is turning into a saga.

Should have said, my mechnic does not have the diagoistic computers.

Thanks in advance. 

I had a similar issue a few years ago although not a ford but never the less after replacing the offside ring I found my issue cropping up again just a few days later only to discover their was a very fine crack in the nearside so decided to replace only to find on removal it just fell in half but fitting the new one cured it without the need for clearing the codes as they automatically cleared once i'd driven my car just a few miles .

Thanks the reply.  This my issue.  Do I go ahead and replace the offside hub and see if it remedies the issue, or have the fault read again first.  It annoys me that they charge £35 to plug a lead in..!