0.0% oxygen content is actually very good IF all other emission numbers are within their averages. It means your VW Jetta used up all it's oxygen during the combustion and catalytic operation processes. If NOx was high, CO very low, and O2 low as well, it might indicate a lean fuel condition. Neither says your VW Jetta's catalytic converter is defective however. The trouble code is a different story. If your Jetta's check engine light is on and the trouble code indicated a CAT Efficiency Code we'd recommend first inspecting the rear O2 sensor and then the catalytic converter. A "lazy" rear O2 sensor will trigger a CAT Efficiency trouble code without the CAT actually having a problem. Given the cost of replacing the CAT as opposed to the Oxygen Sensor, we recommend making very certain which component is actually defective.
As far as the rear (or front) O2 sensor being disconnected during the smog check... If either O2 sensor was unplugged during the smog check the check engine light would have turned on instantly and your Jetta would have no chance of passing the smog check.
