2005 Honda Accord Oxygen Sensor Repeat Replacement

If the diagnosis was made using nothing more then the CEL trouble code and they just replaced that part, it doesn't mean a poor diagnosis. You did say the O2 sensor was broken, so did you mean physically broken or just stopped working? There is a big difference between those two words. Also, brand new out of the box parts have been known to be non-operable right out of the package, because in most cases every single part produced is NOT tested, the usually take them off the line at random and do tests on them. So if the first one was "burned out", not broken, and the replacement your mechanic put in the second time(third sensor) free of charge, stopped working, obviously the converter could or would be the cause, so if the second one simply burned out, common sense should tell a mechanic to check the converter as the cause. Certain car makes and models seem to just "eat up" O2 Sensors, while others never have a problem at all with them, which may actually indicate a design flaw in the systems, which almost no manufacturer will easily or voluntarily admit to. The FIX for a faulty or bad catalytic converter is to replace it.

Thanks for helping me to understand that. I'm not sure if the part looked physically broken or if it just stopped working but looked ok. I don't yet understand why a broken catalytic converter would break multiple O2 sensors though. Wouldn't the O2 sensor just tell you the O2 levels weren't right?

The O2 sensor is one of many sensors that work to tell the cars computer things like air temperature, air flow and many other types of readings in addition to the exhaust fumes being either high in or low in oxygen content, and the computer is constantly changing the air flow and fuel mixture, and how long of an electrical pulse to the fuel (how long each injector stays open allowing the flow of fuel to each cylinder), injectors to emit the lowest possible amount of toxic fumes being released by the engine. The catalytic converter has certain elements inside it that the fumes pass thru which, further reduces the amount of pollutants released into the air. When a catalytic converter "breaks", it usually has broken down to the point where the elements stop doing their job with the fumes being emitted, or it can physically become clogged, and the fumes cannot pass through it and that eventually makes the O2 sensor "burn out", or stop working. This is the simplest explanation I can give you that a normal person can understand, and I am sure it is not as near to everything these sensors and converters actually do, but it should help you understand. So basically, if the elements in the converter break down and don't do their job anymore, it can cause the sensor to burn out and stop working then the sensor would need to be to be replaced. Since this has happened to three sensors now, it stands to reason that most likely the converter has failed which causes the sensors to fail, so the converter needs to be replaced or it will keep burning out the sensors. The O2 sensors do more than just tell you the O2 levels are out of adjustment, and are constantly taking readings and telling the computer to make adjustments and over time the entire process could then cause other sensors and input output monitors to fail or set other trouble codes. A "bad" converter can actually keep the car from running at all, and if it is clogged bad enough it can get so hot it can set the car on fire.