Intermittent P0420 Check engine - Catalytic Converter replacement?

$288 for a new aftermarket Walker cat makes more sense without risking your eyes, lungs or liver, probably for nothing based on reports and shops who have tried chemical solutions.

If you think about it, an industrial quality cleaning system that actually restored a bad cat could make more per oem cat as “rebuilt” than the $300-$500 metal recyclers pay for a $1800 oem unit.

Besides those points, every backyard mechanic knows about the o2 cheat to eliminate the code most of the time. But you still risk engine efficiency or damage running a clogged cat.

 

Yeah I wasn't sure whether this was the guy from Slovakia or California apparently California which is just as bad as far as the laws goes with cars and things apparently

 

Probably not (much) better. Any decent OBD2 scantool can show ECM data for fuel trims, and both Air-Fuel and O2 sensors.

If you really understand what you're looking at, you can see if the sensors are working correctly and what the converter is doing.

There is additional testing you can perform with an "OE" level scantool that has bidirectional controls. Again, you need to understand how the system works in order to make sense of the data.

(If you want to "fully" diagnose this yourself, you'll need to get seriously educated).

My advice is to look at Short Term and Long Term fuel trims while driving the car. If (ST + LT) stays at 0 +/- 10% under "all" conditions AND there are no engine misfires AND there are NO exhaust leaks anywhere near the cat or O2 sensors, THEN you need a new cat.

Posted via the PriusChat mobile app.

 

The reason I mentioned the Portuguese paper is because all the shop solutions (paint thinner etc) are dangerous but citric acid and oxcylic acid are as safe as acids get in a 1 mol solution heated it will clean out the carbon clogging without being able to damage anything else. It's a solution that you can use as long as the ceramic is intact.
It's science ;-)
terramir
PS: over on ecomodder is a post of someone successfully trying the method Restoring old catalytic converter's efficiency (cleaning method) - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

 

Definitely have to be clear on what's wrong with the cat. If it is clogged and impeding exhaust flow (often because the former 'honeycomb' has melted and is now a blob), there's not much to do but replace it.

If it is passing exhaust gas just fine, and only not catalyzing it, the citric/oxalic treatment reportedly may help.

Have to take it off the car for that anyway, so it shouldn't be too hard to check which condition applies.

 

Sure is but it has worked for me on 6 different vehicles and have yet to replace a cat.

How is it you know the sensor is working if you get the P0420? /are you saying it is not possible that the sensor has fried?

 

The test that the car does when deciding whether to report P0420 is pretty reliant on a working oxygen sensor. You certainly can't have a fried sensor whose output is always too high or too low, because the test has two steps, one where it makes the engine run extra lean (and has to see the oxygen sensor reading go lean because of it), and next where it makes the engine run extra rich and waits to see the oxygen sensor reading go rich because of it, and measures how long that took. A good catalyst has stored enough oxygen that it takes a while for the sensor reading to go rich, so if that happens too quickly, the cat is judged too low-performing and P0420 is set.

You can see how it is difficult for that test to even complete (with either a pass or a fail) if the oxygen sensor isn't doing its job. Only a test that completes and shows too little oxygen stored in the cat sets this code. A test that can't complete doesn't.

If the car is showing any of the other trouble codes that are specific to an oxygen sensor problem, it doesn't even bother trying to run this test.

 

Anybody on the internet can make that claim that replacing the O2 sensor fixes their P0420 code. 99% of the time, a P0420/P0430 code indicates a good sensor. The rest of the codes like bad heater circuit code indicates a bad sensor.. it's common for the upstream to fail compared to downstream since it's exposed to the burnt oil and very rare for the downstream to go bad (they eventually go bad due to age).

 

Well do not know what to tell you. I am laying claim on the internet that it fixed them 99.9% of the time.

 

Are you saying you know of a thousand Prii that gave a P0420 code and only one of those had a catalytic converter with low oxygen storage capacity?

 

My bad . . . 99% of the time.

https://www.kbb.com/obd-ii/p0420/#causes

See the 6th cause in the list

 

So you are saying you know of a hundred Prii that gave a P0420 code and only one of those had a catalytic converter with low oxygen storage capacity?