Just came across this thread after a search as my TD5 oil light has started to flicker on idle.
When I picked up the landy a few months the oil light came on on the way home. After stopping and checking the oil level, which was fine, the light stayed off the rest of the way home. I gave it a full service and not seen the light on since when running.
On Sunday I wanted to investigate some leaks and jetwashed the engine.
While doing the passenger side, behind the turbo and onto the gearbox I noticed a long single wire which I lifted up and pulled a bit. This seemed to come from near the turbo and go back behind the engine. I didnt trace it and thought no more until reading the comments above.
What is the wire and is it possible it could cause oil light to flicker on idle?
Its only started again after the engine clean and the oil is well topped up and pretty clean.