I've got a vz,had check power train on for few months,took to mechanics they chucked the machine on came up with injector and coil,got it fixed still had powertrain come up on dash,that was about 6 weeks ago got me brakes and rotors done too,well yesterday driving waiting at a round about,smoke pissing out me bonnet and a heap of oil spilled under me car at front passenger end,turns out it's me head gasket
Is the head gasket idea your take on the oil everywhere or the mechanics.
I doubt a head gasket would produce that much oil (but of course I have bin wong before)
I would be degreasing then looking further
An oil pressure switch could blow and they are prone to problems, and as already mentioned, maybe the O ring in the filter housing but doubtful,
as well as auto hoses (pink/red oil) and power steer hoses (pink/red oil again)
Time to buy a couple of cans of degreaser from Superthief, Ripco, Auto Barn etc
Do it when the engine is cold.
And don't saturate/blast the engine with the hose, simply a gentle spray
For codes/warnings I use a scanner I got from Aldi for $50, works for me.
Last I saw I think Ripco had one for $80.
FWIW the one time I let a mechanic scan my VZ he came up with left front wheel sensor, so I replaced the oil pressure switch and no more problem.