ESP engine management light

[Andrew_26]

Hoping someone out there can point me in the right direction to solve the fault i'm having with my '09  Mondeo 2.0 ltr diesel TDCi. 

The engine management light comes on and shows fault with ESP, the car then goes into 'limp' mode.  Now i've narrowed this down and it only happens at certain times, and it seems quite specific. So when its been parked for an hour or more , you drive off and if you can join an 'A' road or motorway within say 5 minutes, you accelerate, and as you reach 40-50 mph the light comes on. This has happened several times , using same circumstances, so far this week. 

If you drive off with out encountering a main road straight away, and say, stay  on a 'B' road for a while, then later, drive on a main road after, say 15-20 mins or more, it doesn't happen!  

When the light does come on, if you pull over, turn off the engine then re start you can drive on normally without the light coming on again, main road or not. 

I've taken the car to a couple of garages without no luck of positive diagnoses. When put on test, one garage threw up issues with ABS/ BCMII/ PCM . The other garage said maybe an issue with steering angle sensor.  Neither garage seems really confident of their findings , and spoke of lots more fault finding needed (money!) and afterwards , maybe still not finding the route of the problem. So no confidence there!

Hoping someone out there has had some experience of this issue and can point me in the right direction. The car's in great condition apart from this frustrating fault .

One last thing , fairly soon after we bought it , we went on hols in it and did over 2500 miles , without the light issue. When we came back we had the cambelt replaced as we could find no history of it being done in the paperwork we had, together with the drive belt. The light issue showed itself a week or two afterwards, does anyone think the warning light problem could be linked or just coincidence?      

Many thanks in advance