Originally Posted by mar5168

If you listened to me you'd have a vehicle that was fixed properly the first time.

Please re-read my post to answer your first question. I didn't recommend anything. I did, however, provide factually accurate statements, my hunch as to what's causing the problem, and information on how to fix it.

Do you have any empirical data to back up your claim that replacing downstream O2 sensors is the fix for a catalyst inefficiency code?
Remember, correlation does not equal causation.

I know this may be hard to understand, but your p0420 and p0430 were not fixed by replacing downstream O2s. The codes simply never set after you cleared them when you replaced the sensors. I do, however, have no doubt that your exhaust leak could have caused catalyst inefficiency codes as this is very common.

Because of the sensitive nature of catalyst inefficiency code logic (dictated by the gov, and different in California), every dealership I've worked for has a policy of clear and wait for re-code on P0420 and P0430. Interestingly enough, I'd say less than 1/4 of vehicles would re-code and require additional diagnostics.

As a side note, 99% of career technicians I've worked with are looking out for the best interest of the customer. I, in no way shape or form am trying to dupe people into pointlessly spending money. Most of us take pride in accurate first time diagnosis and repair (a common metric in the industry). Stating I'd cost you "several grand" and am part of the reason people work on their own vehicles, shows your misunderstanding for the industry, my post, and myself personally.

I could very easily make the argument that listening to somebody uneducated in the field of automotive repair that's recommending replacing downstream O2 sensors for a catalyst inefficiency code is the easiest way to waste "several grand", require multiple repairs, and is reason to have a professional look at it.




I'm glad that you're both aligned on your logical fallacies, but allow me to provide some actual facts as opposed to the tribal knowledge being passed around. Catalysts do, in fact, go bad over time. The catalyst substrate is made of platinum, palladium, and rhodium. Heat cycling of the substrate causes it to break down over time and the microscopic parts or platinum, palladium, and rhodium get shot out of your exhaust. So yes, prolonged loss of substrate material does mean the catalyst becomes less efficient over time, which obviously, can result in the codes being thrown.