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Discussion Starter · #1 · (Edited)
So I just had my engine bay O2 sensor replaced at a local shop. That service was done and then when the shop ran some VAG test, got this new error. They told me the Catalytic Converter appears to be an issue and recommended I contact VW to get that looked at. In California there is a Federal/California law for 8 year 80K miles for certain emission parts so the Cat supposed to be covered. I am 59K miles and it is a 2010 so still have time. I made my VW appointment and will see how it goes.

Anyway, anyone else ever get this error? Was it the Cat? Did your state have similar extended warranty on this and did VW take care of it, no charge?

I have to pay VW $99 to inspect and then if indeed it is a extended warranty emission issue, they supposed to take care of it. We will see.

Not sure with the O2 just being replaced if it needs a period of driving before the Cat cleans itself out (not sure how that all works) or truly shows the Cat is on its last leg. So far the O2 sensor CEL has not come back but.... I worry the CAT is indeed flaky now.

TJ
 

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P0420 is an industry standard nuisance.

Often the problem can be the catalytic converter, VW did have some problems with certain units.

But also things like an engine running too cold, exhaust leaks and other things can cause false P0420.

You really need to spend $30 and get the OBDFusion App and the proper interface for your phone or tablet. You will be able to see everything that the OBDII system is capable of showing, to include Engine Coolant Temperature and you can Log the Post-Cat O2 sensor behavior and see how well the catalytic converter is working.
 

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Discussion Starter · #4 · (Edited)
Hi,

I do now own the OBD Fusion but other than reading some recent codes for O2 sensor, I have not explored all the other things it can do. I think what I will do is try that this weekend and postpone making a VW appointment until I get another CEL.

No manual, that I know of, shows all the functions of this iOS software so may be hard to understand its full use. I have emailed the company asking if they have any .PDF manual. Meanwhile, I am guessing as a non mechanic, what I am needing to run to check conditions on how the Cat is doing.

So any advice on that would be cool, if you use this software that is.

Maybe my local shop was jumping the gun and recommending I do it before that 8/80 is up. There was little time between them replacing the O2 sensor and not mileage put on since it was done.

And as of right now no new CEL so not sure if I should give it some time.

He seemed fairly sure the cat was bad but, who knows.

Am I correct that if the CAT is bad, and not clean enough per what it was programmed to do, that the CEL WILL come on?

Or that this P0420 should come back soon if emissions are off?

Or does CEL only come on if the sensors that check for this stuff go bad and not state the real condition of the cat itself?

My local tech seemed to thing I will get a CEL soon but..

Thanks

TJ
 

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Discussion Starter · #5 ·
Is there some place thought that can explain these readings, to a non mechanic? I own the app and can explore #s... But knowing what ius good or bad may elude me.

Is there some chart that will show what these readings "should" be?

TJ

P0420 is an industry standard nuisance.

Often the problem can be the catalytic converter, VW did have some problems with certain units.

But also things like an engine running too cold, exhaust leaks and other things can cause false P0420.

You really need to spend $30 and get the OBDFusion App and the proper interface for your phone or tablet. You will be able to see everything that the OBDII system is capable of showing, to include Engine Coolant Temperature and you can Log the Post-Cat O2 sensor behavior and see how well the catalytic converter is working.
 

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Discussion Starter · #7 ·
Just thought I would finalize this thread and did get that O2 sensor replaced. Had it done by a shop. I did not want to tackle this one. That with my 10K oil change came to about $330 or so. No CEL now and all seems well. That P0420 error did not come back so even though they saw it after replacing that O2 sensor, 1K miles later, no errors appearing on OBD reader. So not sure they needed to run the beetle longer and hotter after replacing the O2 or what. They expected that CEL to come on soon and now all tests show things are fine. Maybe the beetle was not running great for a bit with that O2 sensor being bad and it needed some time after the service to get back to normal. Not sure but it appears good now. tj
 

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If the exhaust has a leak of the converter is compromised, you can EASILY trigger the P0420 code by driving on the highway and find a stretch of road that is flat or slightly down hill. P0420 typically will trigger if there is a problem while coasting or on very light throttle at highway speeds for 20-30 seconds.

If there is a problem, a 10-30 minute highway drive where you can go into a very light throttle under a slight downhill coast and the P0420 will typically pop.
 
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