Wipers / Tyre Warning / DSC - what's the connection?

[rdun2004]

HI. I have a 2005 X5 3.0d, great car.

About 6 weeks ago I got a tyre pressure warning - all OK so reset. It repeated about a week later - all OK so reset. About 3 weeks ago the amber traction 4x4 light came up and would not go off, turning engine off / on or pressing DSC button made no difference. Pressing and holding the DSC button put the light out. At the same time the speed and rain sensitive wipers stopped working, they would make one wipe and then stop.

So now I have no warning lights but no intermittent wiper function; it would work when first started but then when speed exceeded 20mph would stop and stay stopped until the car was left for an extended period of time (day / night).

Since then I have had a local independent garage run diags - they found nothing. After the diag the intermittent wipers worked! Until half way home and then the tyre pressure warning light came on and the wipers stopped (they work and always have worked when on continuous). Checked tyres - OK so reset. Intermittent wiper problem the same - works when car "freshly" started and then stops when speed exceeds 20mph.

Yesterday and today - same problem. Both mornings - when nearing work and pulling off a dual carriageway towards a roundabout - I thought I would check braking (concerned about ABS involvement). Braking aggressively but not enough to get a skid or invoke ABS (so not that aggressively) all felt fine - and immediatley the intermittent wipers started to work! Both days - 2 tests.

My gut feel is that it is a speed sensor on one of the wheels. Without a warning light on (about DSC or ABS or anything) all main "safety" systems should be OK. Right? How might I diagnose this problem? Do I need to go to a dealer? Can I test each wheel sensor myself?

Appreciate any steer.