Mazda Repair: Madza.. check engine light is on.. what to do when failing emission test.., emmisions test, emissions test

Question
Hi

I have a Madza 2000 Protege.  Car has been running ok but it failed the emissions test for 2006.  Have to take car in for inspection but need to ask a few questions.  My car is starting to skip, had a tune up last year do I need to do this every year?  Also, the check engine light comes on and off has been doing this since last year.  Mechanic just said the sensor was off and he said he fixed it, but it came back on within a week.  It goes out for a while, but within days comes back on.  What should I ask the mechanic to do when I take my car into the dealer?

Thank you
P. Brown

Answer
Hi phyllis thanks for asking
usualy when a check engine light comes on and goes off, the more common reason i see is a bad oxygen sensor, this will definitly be the cause in a failure on the emmisions test. Take the vehicle to someone and have them scan it, the code will be stored i the computer regardless if the check engine light is on or not. But if the code reads a problem with the cat effieceny then the catalytic converter will have to be replaced. these are very expensive so I hope the best for you
Good luck
Chris P