PO520 $18DAF110

Alfa romeo mito 1.3 diesel has oil pressure sensor problem (PO520 $18DAF110) with eml coming on even though cleared faults !! Changed timing chain oil pump fuel filter oil (c2) oil pressure sensor map sensor and everything else that's obvious including oil reset !! My experienced mechanic can't fathom it after weeks of his own time looking!! Car has 88k and in excellent condition!! Just bought wiring loom but not fitted as yet
Just eml no oil light or any other codes