About 125,000 miles on it. Owned it since 90k roughly. Every once in a while the engine light would blink on, seemingly random (solid 55 straightaways, usually), then on next day startup or so, would be off. This time it turned on about a week after my last oil change (due for another soon), and has been on since. Had the code checked and it's the same one it's always thrown when I go to have it checked. First guy (bout a year ago) told me system too lean- took out the mass air flow sensor and cleaned it out, was just fine after. Now, someone told me Cat converter is clogged- this is just off of reading his code reader and seeing PO420. Dunno how accurate any of that is.
I'm wanting to know the reason and what I should do in steps to figure it out before I go dumping my money into incorrect solutions.
-I don't know a whole lot about cars, or a good mechanic around here as I recently moved.
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PO420 suggest the catalytic converter isn't working as efficiently as the computer would like it to .. Possible cause is faulty downstream 02 sensor OR depleted catalyst inside the converter .. Your car is a Toyota Corolla that's called a Prizm! .. Code PO420 has been in my Toyota Camry for about 5 years now, not effecting performance or fuel mileage .. When it does so, I will consider fixing it .. We do not have emissions testing here and you probably don't either .. I work on em for a living and have done so for over 43 years now .. I have a high dollar scanner that I test my vehicles with so I know what's going on .. You can buy an inexpensive scan tool nowadays so you can do the same in case another problem comes up .. Just scan the system for codes every now and again... Now there are going to be PLENTY that disagree with me on this but I'm telling you what I know as a fact! .. You decide IF you want to spend the money it's going to cost to repair this issue with the check engine light.. BTW, the code reader/scan tool will also clear the codes and turn off the C E L .. Good luck and happy motoring.
