Catalytic converters can and do wear out, even under perfect operating conditionsMaybe not for every car, but it does happen
I am not saying that is the case here, but it is a possibility
I agree that they do wear out. One study I ready by some consumer group stated they found that well over 80% of catalytic converters that were replaced were in fact NOT faulty.
“well over 80% of catalytic converters that were replaced were in fact NOT faulty.”
I agree that some cats are replaced, when the real cause of P0420 was something else
But I’m not sure I agree with “well over 80%”
I wonder how that group came up with their numbers
The frustrating thing . . . for the car owners . . . is that you can have a situation where the cat itself is indeed “faulty” enough to legitimately set P0420, yet the car seems to be running exactly the same as before.
And then you can have the opposite . . . a cat not clean enough to pass the tailpipe test, yet no P0420. Yet the car does not have the classic symptom of poor acceleration, due to a plugged exhaust
I think there’s also a very large gray area, where you’ve got an aging car with high mileage, original cats and sensors, and a P0420. You replace the sensor(s), clear the codes, let the monitor run and pass. But it BARELY passes. And the old cat gets bad enough in a few weeks or months to set P0420. And then the mechanic is accused of doing poor diagnosis, because he “didn’t see it coming.” What’s more, he’s accused of needless selling the sensor(s), which in some cases aren’t that cheap. That’s where mode 6 data comes in. Because if he looks at that data, he CAN see it coming.
But I'm not sure I agree with "well over 80%"I wonder how that group came up with their numbers
Not sure either…But I wouldn’t be surprised of the 80%. Remember that not all mechanics are honest like you seem to be…Especially the national chains (Midas, Sears, NTW…etc). And unfortunately they do a good chunk of mechanical work in the US.
If original plugs change them. Needs to be done and may clean up exhaust enough to stave off the error codes
I am aware that the platinum-palladium (catalyst) sputter-coated onto the ceramic substrate doesn’t actually wear off the substrate but rather becomes coated with exhaust components that prevent intimate contact of the oxygen atoms in the NOX component of the exhaust with the catalyst, preventing the oxygen atoms from being stripped from the NOX molecules, but I’m perfectly comfortable with the term “wears out”. None of the blather I just wrote provides any contribution to solving the problem.
Jeeze, guys, it may very well be this arguing amongst ourselves about meaningless details that don’t contribute to a resolution that drives visitors away.
I agree with db’s post above that while some converters are changed needlessly I think 80% is way too high an estimate. Often a sensor will be replaced and the CEL disappear for a while, but the converter end up being changed anyway. Converters do eventually become inefficient. They are, after all, subject to anything and everything in the exhaust stream, and there’s no such thing as a perfectly clean exhaust stream. If the “low efficiency” codes present on a Toyota over 150,000 miles, it’s not imprudent to change the converter.
The ones that I would be highly suspect of are the ones that store the codes on engines well below 100,000 miles… unless, of course, it’s all NYC miles.