cheers ill try an oil and filter change first and a flush , then have a look at pressure sensor, suppose i may aswell go for the breather aswell as it can only help if it hasnt been done before

working on my cousins 2002 x5 3.0d turbo his batterys been flat for about a month, i took it into work replaced the battery and then on the journey home when i stopped the oi pressure warning came up with the oil light, i stopped checked the oil level which was on max, started driving again fine ...

im not 100% as autodata isnt showing p1 codes, but usually bank 1 sensor 1 and to do with fuel my first guess would be lambda sensors, have you cleared them and they stayed off? or have they came back ?