Review on 🔌 Denso 234-4233 O2 Sensor by Brad Mastermind

I have a 2003 Corolla LE and have had many issues over the years with the P0420 Catalyst system performance below the bank 1 threshold code and after it came out recently I have it bought trying to fix it. I replaced the oxygen sensor with another one from Amazon (sold by TheBigDeals) a few days before purchasing which has not gotten rid of the check engine light or code. I did a little more research and found that it might be because I had to use an OEM sensor. This OEM Denso sensor worked and I had no check engine light AND PASSED MY SMART TEST! I'm so happy I don't have to replace the catalytic converter which can cost thousands of dollars + repairs. If this can help you if you have a 2003 or 2004 Corolla and it's not working for you, I found that there is also a Technical Service Bulletin from Toyota that is issued about a repair they are doing for this problem which requires a "reflash" " computer in the car and costs about $100. It seems to have helped some people and I will now do it as a preventive measure despite going through smog. Here is exactly what it is. https://www.discountconverter.com/tech-tips/news_page.cfm?Key=catalytic_converter-&News=228http://tsb.deccats.com/TSB-3290-corolla-03-04.pdf Other common causes of code p0420 error from what I've researched is exhaust leak, dirty mass air flow sensor (see "walaxvw" answer here http://www.fixya.com/cars/t1056719-p0420_code_toyota_corolla) and I also read " dirty connectors, dirty fuel injectors, or excessive carbon buildup in the combustion chambers." I've also tried Redline Fuel Cleaner, Guaranteed to Pass, Cataclean, and Seafoam, and the codes and check engine light persisted until I replaced the (lower) oxygen sensor on the OEM Denso replaced. .