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P0420

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4 years 7 months ago #33200 by ontheriver
P0420 was created by ontheriver
08 elantra,2.0, trying to get rid of p0420,found a small leak in exhaust pipe in front of #2 o2 sensor,put new pipe on,cleared code, watched live data,rear o2, staying steady now,and of course, light came back on,what puzzles me,is after clear code,it still shows a pending code,so last night I unhooked battery for 5 minutes and my friend went on his way,I'm expecting him back with a light on,so is my scanner not good enough for a Hyundai?is 5 minutes enough?thanks in advance

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4 years 7 months ago #33201 by Tyler
Replied by Tyler on topic P0420
So the battery disconnect did the trick? If so, it might be a scanner issue. Some YMM's are also picky about which codes they'll let you clear without a key cycle and test drive.

It might also be that the ECM still isn't happy with the catalyst performance. :silly:

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4 years 7 months ago #33209 by ontheriver
Replied by ontheriver on topic P0420
Don't know if it did the trick,he came back from a failed inspection, monitors we're not complete,so iscanned it,p0420,was the code,so I checked monitors,and catalyst monitor was incomplete?that's when I disconnected battery,he was in a hurry,had groceries in the car,so we said,see you tomorrow,that's where we're at,I just didn't like what I saw,conflicting info

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4 years 7 months ago #33214 by ontheriver
Replied by ontheriver on topic P0420
Ok,he came back,light on,420,all monitors complete,freeze frame showed nothing out of the norm,a/f sensor holding at 1.9,#2,02,staying at the high .6,did see temp. at 186,is it that finicky,and load % was in the high teens at idle,higher than I expected?

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4 years 7 months ago #33216 by ontheriver
Replied by ontheriver on topic P0420
We are going to replace thermostat, probably original,plus get some fresh antifreeze in there,and I'm know leaning towards replacing cat,but not seeing true evidence, thought did come up to add a extension on for #2o2,get it out of the stream a bit,only cause I read on a site that some are very sensitive and a flash was needed to relax the sensitivity?

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4 years 7 months ago #33217 by Tyler
Replied by Tyler on topic P0420

ontheriver wrote: Ok,he came back,light on,420,all monitors complete,freeze frame showed nothing out of the norm,a/f sensor holding at 1.9,#2,02,staying at the high .6,did see temp. at 186,is it that finicky,and load % was in the high teens at idle,higher than I expected?


Fuel trims within 10% at idle and under load? No more exhaust leaks? If so, then it sounds like that cat is done.

The Load in the teens at idle isn't unusual, in my experience.

thought did come up to add a extension on for #2o2,get it out of the stream a bit,only cause I read on a site that some are very sensitive and a flash was needed to relax the sensitivity?


Eh, you might have luck with one of those extensions? :silly: I see them on customer cars, and it's hit or miss. They either don't work, work, or replace the P0420 with other codes.

I didn't see any TSB's for this car and catalyst codes. Usually, if an OEM has an emissions problem, they publish it in a TSB.

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4 years 7 months ago #33220 by ontheriver
Replied by ontheriver on topic P0420
Thanks,yes fuel trims were low,mostly adding, but 5,,% or under,and also,thanks, didn't know particulars with this vehicle on load%, just thought it should be lower,this is a California emissions vehicle,4 banger,2 cats,resonator and muffler,poor thing,how can it breathe,lol

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4 years 7 months ago #33272 by ontheriver
Replied by ontheriver on topic P0420
So went thru everything,he was neglectful,air filter,mouse nest,pcv valve,filthy,20 squirts with carb clean,it's back,the leak in exhaust,typical flex joint,small leak,but in front of #2,02,all that done,she purrs,with a 420,saw dips down to .1 on o2 on test drive,cat is on order

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4 years 7 months ago #33276 by Tyler
Replied by Tyler on topic P0420
Sucks. :( The Cali emissions replacement cats are always more expensive, too.

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4 years 7 months ago #33279 by ontheriver
Replied by ontheriver on topic P0420
Yep,ouch,and we only ordered the front one,not sure about the second one,any test procedure?it gets up and going fine

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4 years 7 months ago #33281 by Noah
Replied by Noah on topic P0420
There's not always a sensor downstream of "extra" cats. If there's not a sensor behind the second cat then it shouldn't be able to set a code for cat efficiency. :)
"Ground cannot be checked with a 10mm socket"

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4 years 7 months ago #33299 by ontheriver
Replied by ontheriver on topic P0420
Yep,no sensor,but still curious on it's role in the system,and is it up to par?

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4 years 7 months ago #33342 by Tyler
Replied by Tyler on topic P0420
Any 'extra' catalysts after the downstream O2 are still there for emissions purposes, despite not being monitored by the PCM. The only way you'd be able to tell if it's working or not is a tailpipe test with a five gas analyzer.

Does your state do tailpipe tests? Or just OBD compliance? If there's no tailpipe testing (or no emissions testing at all), and the catalyst monitor passes, then it's all good. :)

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4 years 7 months ago #33344 by ontheriver
Replied by ontheriver on topic P0420
Upstate NY,no sniff here yet, coming soon, probably,lol

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4 years 7 months ago #33526 by ontheriver
Replied by ontheriver on topic P0420
Update,got new cat,what a pain,no brick and mortar store would sell me the correct cat, California cat,not on anybody's parts list,federal,yes,but different setup,so,had to go online,buy one and ship it to Vermont, just east of me,cause NY and California and Maine,have the same rules,no federal allowed here if it's California emissions,wow,so it's being driven,hoping for news this afternoon,and I called a manufacturer,and they said,it's the same cat,just c.a.r.b legal

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