I have a weird problem with my 2005 Mazda MPV Van that I am hoping that someone here can help me with …
The vehicle runs fine, but recently when I took it out for smog test, I was told that smog test cannot be performed, because one of my monitors (the one for catalyst) was not ready. Apparently, here in California, the first step in a smog test is to check the status of some monitors from the OBD-II connector and if the status of all monitors is not ready then the smog test cannot proceed. In my case, the monitor showing the status of the catalyst (catalytic converter) was not ready, though there was no check-engine-light indicator lighting up! The smog test person thought that it was happening because I changed my battery recently - which I did not. I was advised to drive the car for some more time and then come back.
Unfortunately driving the car even a few hundred miles did not fix the problem.( I bought a cheap OBD-II monitor and now check the status of these monitors often!). I was then told that Mazdas need to go through a complicated drive cycle to get these monitors ready. I downloaded many instructions from the internet and went through as many drive cycles as I could ( usually they involve driving the car at various speeds in a sequence). But no matter what I did, I couldn’t get the catalyst monitor ready for smog check!
Finally I took the van to the local Mazda dealership. They tested it for a day, informed me that they called up Mazda’s engineering support, and following their procedure determined that an oxygen sensor was faulty. I got them to replace that sensor. I was then informed that I need to go through the same complicated drive cycle again to get the monitor ready 
. So after a few more days of driving around and a few drive cycles later, I still don’t see the monitor getting ready.
The dealership wants me to bring the car in again. Their guys also seem to be not sure what the issue is. ( They want to now see how the other 3 oxygen sensors are doing… ) I am beginning to lose confidence that they can even diagnose the problem. I am desparately hoping that someone on this board has some experience with such a problem!