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2002 Toyota Corolla Failed Catalytic Converter

My 2002 Corolla passed its smog check two years ago, but just a week after I passed it, my check engine light came on. My mechanic said it was a failed catalytic converter. How could that be if I just passed the smog check? The check engine light went off after a few months and stayed off for well over a year. It just came back on, in time for another smog check. What are the chances that my converter actually does need to be replaced (since it seemed to pass last time) before another check? Will it fail anyway since the car's computer says the converter has failed?

Answer:

Without a hands on diagnosis there is no way of telling if your Toyota Corolla's catalytic converter is bad or not. The check engine light could illuminate and set a catalytic converter efficiency trouble code however the CAT needs to be physically inspected. Often a defective rear oxygen sensor (the one that tells your Toyota's computer whether the catalytic converter is functioning properly or not) is defective itself. The fact that your Toyota passed the last smog check does not necessarily mean it will pass this smog check as well, especially if the check engine light is illuminated. Your Toyota Corolla can not pass the smog check if the check engine light is illuminated during the smog check or any time up to one month prior to the smog check (assuming your drive at least 1000 miles a month). posted by SmogTips Support

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