We have a 2004 XC70 with non-working AWD. I replaced the AOC pump/filter/fluid and the AWD still didn't work. Not wanting to rebuild my DEM if was just the pressure sensor, I went to my local euro car shop and they pulled a DEM code for "Differential oil pressure improper value". They cleared the code and my AWD works now. Is that really how it works? Once the code gets thrown, it just doesn't work anymore until you clear it? Surely it would clear at the next key cycle, right?