I had this with a 1.9dti scenic, it turned out to be a loose earth strap from the body to a 10mm bolt on the intake manifold!!
go figure? the main earth strap on the gearbox to battery was good.... but even the AA diagnostic said it was a master relay fault, never did find a master relay!! after fixing the earth strap to manifold it went fine, nothing else was done!
spud
February 2016