2000 Taurus V6 DOHC. Idles good, runs good but bogs down other times. Shows no OBDII codes. Won't pass smog check because no memory in PCM. Drove it for 2 more days after smog check, still no memory in PCM. Check engine light is off. It is on before engine start, turns off after engine starts. OBDII reader connects and states, no codes to read. This is a well maintained car without any other issues. I'm thinking that maybe the PCM doesn't complete a diagnoses and hangs up. If any one else has had this problem and knows the fix please advise me.