The Duchess, our 97 VDP showed a Check Engine light, code was P0326 (knock sensor) about two years ago, which was cleared by my local friendly auto parts store (back when they were still permitted to do so), and she later passed the annual DMV inspection. Then the same code reoccurred over a year later and recently cleared code with a U380 OBD-II Memo Scanner. But now, even 500+ miles later, the inspection machine says the Catalyst, EGR System, Evaporation System and O2 Sensor are “Not Ready” on the inspection printout, so she can’t pass. She’s drinks nothing but premium fuel and runs great, so there’s no knocking problem. BTW, while Heated Catalyst and A/C System measurements are showing “Not Available ” on the printout, Misfire, Fuel System, Comprehensive Component, Secondary Air System and O2 Sensor Heater categories are showing “Ready.”

What am I missing? What might be different the second time around that would cause the computer to not have data available for all parameters being measured?

Thank you in advance to whoever can provide an answer.