Often times the generics will just show something like a P0700 in the engine, which is the "check the transmission controller for faults" code, essentially. Generic scan tools really are hit and miss, on all kinds of cars, and just generally suck because you never really know if you are getting the whole story. I just fixed a 2003 AWM (1.8t) Passat today that had a blown suction pump (gizmo for the breather system that works with turbocharged gas engines). It came in late last night after I left, and they quick scanned it for the lady with our hand held we keep in the drive through lane (usually just for checking readiness), and it gave misfire DTCs for all 4 cyl, as well as a P0300 random misfire. That's it. But VCDS gave me the P0171 system lean, P0111 oxygen regulation too lean, and a couple other air fuel ratio and idle speed related DTCs.... all of which pointed to the REAL problem of the massive intake leak. The misfires were just secondary, as they were caused by running with too much air (lean misfires). Had I just had the generic, I'd have been in the dark as to the real problem, since the suction pump blows apart internally, so the intake leak is actually due to too much air being drawn in through the crankcase ventilation system.
