Subaru p0420

2010 outback2.5 code p0420. Hi all! Last night after hitting a rough patch of road on the highway most of my dash lights lit up. Cruise and E brake light blinking, check engine and traction came on too. I took it to autozone just to get the code and p0420 Bank 1 came up in the test results.

Prime Pageants creates a completely different pageant experience by helping contestants reach their goals with a cooperative mastermind group. * Required Field Your Name: * Your E-...Code P0420 - catalyst efficiency; code p301-4 misfires on various cylinders - new spark plugs NGK BKR5EGP 018-3645-8 ... (Yes, I have seen this happen on Subaru) Also, such a condition may overwelm the catalyst with too much fuel causing some of your other symptoms. Reactions: Horsehockey2.The nerdy and keen eyed will notice I omitted the valve lash adjustment on these 2008-2010 Subaru products with the 2.5L engine...because nobody and I mean N...The common causes of the P0420 code in Subaru vehicles include a faulty catalytic converter, oxygen sensor malfunction, exhaust leaks, engine misfire, or fuel system issues. These issues can lead to increased emissions levels, triggering the P0420 code which indicates a problem with the efficiency of the catalytic converter.Home SubaruP0420 Subaru DTC P0420 Make: Subaru Code: P0420 Definition: Catalyst System Efficiency Below Threshold (Bank 1) Description: Engine stalls. Idle mixture is out of specifications. Vehicle is driven > 43.5 mph and ECM detected amplitudes signals that are too similar during the test. Cause: Loose or damaged exhaust system parts.=====Claim your FREE engine code eraser 👉 https://free.nonda.co 👈=====Engine Code SUBARU P0457 Saving Repa...

One of my favorite threads for this is the $5 fix :wink: When you get the P0420 CEL code, the cause can be: A faulty or failing front O2 sensor (if your gas mileage has dropped off with hesitation, backfires & an overly sooty exhaust tip). An exhaust air leak ahead of the rear O2 sensor (rusted or cracked pipe). A failed CAT.21417 posts · Joined 2006. #5 · Jul 10, 2014. However, when the light is cleared, while using the cruise control there is a slight hesitation present ONLY while the cruise is being used. There is no hesitation or issue present otherwise. It's possible that the P0420 and the hesitation are related, and that the hesitation is more noticeable ...Welcome to the Subaru Outback Owners Forum, we have tons of information about your Subaru Outback, from a Subaru Outback Wiki to customer reviews. Show Less . Full Forum Listing. Explore Our Forums. Gen 5: 2015-2019 Problems & DIY Maintenance Gen 4: 2010-2014 Gen 6: 2020-present General Discussions.4 days, 1 subaru wideband sensor, and 3 drive cycles later, I have clearing subaru readiness monitors down to a T. And the wide-band that came with my AEM failsafe gauge is looks to be the same model as the subaru wideband, except the resistors are different. But, the P0420 code was still there.2013 Outback P0420 code. Hello, I am new to this forum and Subarus meaning that this is my first Subaru and first post. Thanks for all the great information. I currently have a P0420 code and am trying to determine the issue. I have a 2013 Outback with 121k miles which I bought back in March 2017. There were lean codes which were …Obesity affects our health and earnings. On average, obesity costs an extra $3,439 annually. Here's how to lose weight without losing money. By clicking "TRY IT", I agree to receiv...EATON VANCE GEORGIA MUNICIPAL INCOME FUND CLASS A- Performance charts including intraday, historical charts and prices and keydata. Indices Commodities Currencies StocksAir can and does enter cracks or small holes in the exhaust. A system in good shape does not have measurable pressure in it. The exhaust flowing through the pipe can draw ambient air in through openings. A partially blocked converter won't necessarily throw a P0420 code if it is still working as a catalyst.

My P0420 code started this past February and it has been driving me crazy. I started with replacing the pcv, code still there, then I used the Seafoam method. That cleared the code for a few weeks just enough to help me pass my inspection in August.Jan 29, 2024 · The P0420 code in a Subaru Outback is typically triggered by issues related to the vehicle’s catalytic converter. One common cause is a faulty or damaged catalytic converter, which may be clogged or no longer functioning properly. Another possible cause is an oxygen sensor failure, specifically the downstream oxygen sensor, which measures the ... Jan 6, 2024 · P0420 Code in Subaru The P0420 code on a Subaru often can be triggered by a bad catalytic converter or a faulty oxygen sensor on older models. Look for exhaust leaks as well, as with Honda, replacing your catalytic converter or oxygen sensors and regular servicing can help resolve the issue. Nov 30, 2018 · The most common fix for P0420 in the Subaru Impreza is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Impreza into an exhaust shop for an (expensive) new catalytic converter, let’s ensure that’s what you need. Here’s a good P0420 diagnostic order for the Subaru Impreza: 1. Check for Other Codes. P0420 Subaru: Code Meaning, Causes, Symptoms, & Tech Notes. The Engine Control Module (ECM) monitors the switching frequency ratio of heated oxygen sensors 1 (front O2 sensor) and heated oxygen sensors 2 (rear O2. www.engine-codes.com.The P0420 Diagnostic Trouble Code is a clear indication that your vehicle's catalytic converter is not efficiently functioning. The Catalytic Converter is part of the …

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Here's an Amazon link to that impact gun → http://www.amazon.com/gp/product/B00BWFIKZO/ref=as_li_qf_sp_asin_il_tl?ie=UTF8&camp=1789&creative=9325&creativeASI... May 11, 2017 · So my wife and I bought an '07 Outback Basic back in January, used with about 130k miles on it. MIL came on around 6 weeks ago with a P0420 code. Been doing a lot of googling/reading about P0420 codes lately- I've had several conversations with different mechanics around town, some helpful and some not, but someone suggested that since the only ... As the code description implies the P0420 code means that the vehicle's control module has detected that the three-way catalytic converter is not working properly (is not as efficient as the factory is expecting).Mar 21, 2024 · If you find a P0420 code in your Subaru or Honda, it’s most likely the catalytic converter to blame. It can also be caused by an exhaust leak or a bad oxygen sensor . Check for vacuum leaks or other fuel mixture-related engine codes. The P0420 code is a common issue that many Subaru Impreza owners experience. This subheading aims to provide a detailed explanation of what the code means and its implications for the vehicle. The P0420 code signifies a problem with the catalytic converter efficiency in the exhaust system of the Subaru Impreza.My '11 (140k miles) has been throwing a P0420 code along with running a bit rough, it stalls from a start (oddly the autostart has no issues keeping it running), and I'd say I'm down to about 70% power overall. ... We’re the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability ...

It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may be slightly different depending on the model. So this engine code article applies to Nissan, Toyota, Chevrolet, Ford, Honda, GMC, Subaru, VW, etc. P0420 is one of the more common trouble codes that we see. Summary. P0420 stands for “Catalyst System Efficiency Below Threshold (Bank 1).”. This trouble code is triggered when the on-board computer detects that the bank 1 of the catalytic converter is underperforming. A faulty catalytic converter (usually due to overheating and contamination) is the most common reason why this code is logged.Eight hours a day is way too much at some Swedish companies. By clicking "TRY IT", I agree to receive newsletters and promotions from Money and its partners. I agree to Money's Ter...Prime Pageants creates a completely different pageant experience by helping contestants reach their goals with a cooperative mastermind group. * Required Field Your Name: * Your E-...Jan 5, 2009 · the most common problem for P0420 seems to be a bad O2 sensor. front O2 sensor needs to be OEM at about $100, rear O2 sensor can be parts store brand >$100. I also replaced my sticking EGR valve when i replace my front O2, dont know if that had anything to do with P0420. now it could also be a leak in the exhaust, replacing the gaskets seems to ... Ran my OBD2 scanner and turns out I have a catalytic converter code failing code (P0420). I remember this happening to me about 4-5 years ago but all I did was clear the code and i’m pretty sure it never came back until very recently. So I cleared the code just like I did 4-5 years ago and within maybe 2 weeks the code came back again. Subaru code P0420 refers to a diagnostic trouble code that indicates an issue with the catalytic converter in a Subaru vehicle. It means that there is a malfunction in the efficiency of the catalytic converter, which could be caused by various factors such as a faulty oxygen sensor or an exhaust leak. This code should be addressed promptly as ...Has your check engine light recently turned on? Are you seeing the dreaded error code P0420 on your vehicle’s diagnostic scanner? Don’t panic just yet. Code P0420 is a common issue...Visit me at: http://www.ericthecarguy.com/O2 Sensor Video: https://www.youtube.com/watch?v=NIzcztO-CCsDiscussion about this video: http://www.ericthecarguy...

The P0420 engine code indicates the catalyst system efficiency is below the threshold (Bank 1). A P0420 code indicates a problem with the catalytic converter, more specifically. The purpose of the catalytic converter is to break down harmful pollutants created during the combustion cycle. By using fine platinum and gold meshes to filter exhaust ...

There is a thread on this forum with over 3,000 posts that deals specifically with the P0420 code. The main thing to know is that this code DOES NOT mean the CAT needs replacing. The next thing to know is that the O2 sensors need to be genuine Subaru or Denso brand as other sensors such as Bosch react too slowly for the ECU.Summary. P0420 stands for “Catalyst System Efficiency Below Threshold (Bank 1).”. This trouble code is triggered when the on-board computer detects that the bank 1 of the catalytic converter is underperforming. A faulty catalytic converter (usually due to overheating and contamination) is the most common reason why this code is logged.The most common cause of the P0420 engine code is a degraded catalyst. Catalytic converters/catalysts break down over time and can also become clogged. Cylinder misfires will significantly reduce ...Even slight variations in the air/fuel mixture will cause the converter temperature to rise significantly. The “Catalytic Converter Efficiency” Diagnostic Trouble Codes (DTCs) P0420 and P0430, are among the top 10 DTCs technicians face. And while the description might imply a failed converter, odds are the ultimate fault lies somewhere …The P0420 code is a common issue that many Subaru Impreza owners experience. This subheading aims to provide a detailed explanation of what the code means and its implications for the vehicle. The P0420 code signifies a problem with the catalytic converter efficiency in the exhaust system of the Subaru Impreza.I ran into a code that occurred 3 times now when driving on the freeway only at around 60-70 mph which was a P0420 code. I have been told by fellow Subaru enthusiasts in my area to replace the front O2 sensor, but read on this forum that it should be the rear sensor. On the 2011 LGT, the O2 sensors are close to each other so I really …Oct 30, 2012 · Now, to effectively diagnose the issue with a P0420 using aftermarket software and determine where the problem lies, and we will use RomRaider since it is widely used by Subaru owners for various reasons, log the data from the rear O2 sensor. In RomRaider, click the Rear O2 Sensor and use either Amps or Volts.

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Even slight variations in the air/fuel mixture will cause the converter temperature to rise significantly. The “Catalytic Converter Efficiency” Diagnostic Trouble Codes (DTCs) P0420 and P0430, are among the top 10 DTCs technicians face. And while the description might imply a failed converter, odds are the ultimate fault lies somewhere …Every mechanic has seen intermittent P0420's that come back after months or a year, that's common. A P0420 due to an oil filter is unheard of. More than likely the P0420 was intermittent and was going to go out and come back at some point no matter what you did. H6 OBW VDC, H6 OB Sedan, Tribeca, Lifted XT6. traildogck.The P0420 code in a Subaru Outback is typically triggered by issues related to the vehicle’s catalytic converter. One common cause is a faulty or damaged catalytic converter, which may be clogged or no longer functioning properly. Another possible cause is an oxygen sensor failure, specifically the downstream oxygen sensor, which measures the ...In this video, you'll learn the causes and solutions of the P0420 code. The causes of the P0420 code are a bad catalytic converter, an ECM update, an exhaust... It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may be slightly different depending on the model. So this engine code article applies to Nissan, Toyota, Chevrolet, Ford, Honda, GMC, Subaru, VW, etc. P0420 is one of the more common trouble codes that we see. P0420 is VERY RARELY a failing cat. It is most commonly a failing oxygen sensor (front Subaru, rear any brand), vacuum leak, exhaust leak or what not. Search that code on the forums and you'll find plenty of info. Cats rarely fail without serious mechanical problems, I think your mechanic wants to give you an expensive repair bill.Welcome to the Subaru Outback Owners Forum, we have tons of information about your Subaru Outback, from a Subaru Outback Wiki to customer reviews. Show Less . Full Forum Listing. Explore Our Forums. Gen 5: 2015-2019 Problems & DIY Maintenance Gen 4: 2010-2014 Gen 6: 2020-present General Discussions.NinoS. 1104 posts · Joined 2014. #3 · Sep 8, 2020. I've used them before back when I put headers on my 03X - the fix works. You'll want to take a look at your 02 sensor and make sure you have space for a spacer (or maybe even if you can get it out), might need a 90 degree spacer (i'm not familiar with the SH forester).This low kilometer Subaru Impreza flags a P0420 Catalyst efficiency fault code very quickly. The rear O2 sensor would behave almost like the catalytic converter had been removed. Replacement ...May 31, 2012 · 16442 posts · Joined 2015. #24 · Feb 24, 2017. Alright for future people who find this p0420 is a catalyst failure. You either need to replace the cat, replace the sensor if the cat is good, or ideally have the proper tune on the car so it blocks the code. Sent from my SAMSUNG-SM-G935A using Tapatalk. Jan 10, 2012 · 63 posts · Joined 2011. #1 · Jan 10, 2012. I have a 2004 OBW and it keeps throwing the P0420 catalytic system below threshold code. The car is bone stock. It is drive by wire and has the California emissions on it. It's engine is a model EJ259 if I remember correct. I've tried using the anti-foulers, and even the electronic fixes in the rear ... Hi all, I have a 1999 Outback S/W 95K. I bought it used and the head gasket was changed by previous owner at 86K. Shortly after buying it two months ago the check engine light went off. The code was P0440 - Evap Emissions Malfunction. After searching the internet and talking to mechanics I see it is a difficult problem to diagnose and correct. ….

104 posts · Joined 2008. #2 · Oct 3, 2011. I as well have been dealing with the P0420 and a local subie dealer out here mentioned basically to clear the code and see how long it takes for it to come back up. Meanwhile, run fuel cleaner through the system to clear up the injectors and the 02 sensors. You said your putting the anti-foulers on ...209K subscribers. 43K views 4 years ago. ...more. Ah the classic Subaru P0420. So are parts required to fix this pesky emissions code? In this case we get a good example of where the "money...Sep 6, 2017 · Like. Jay11STI. 3579 posts · Joined 2011. #8 · Sep 9, 2017. P0420 is generally a universal code for Catalytic Converter limit below threshold or something along those lines. P0420 indicates a failing catalytic converter. Correct me if im wrong but all Cobb downpipes are catted and have that high flow cat in them. CAOVF: Get the latest China Overseas Land & Investment LtdShs stock price and detailed information including CAOVF news, historical charts and realtime prices. Indices Commodities ...May 23, 2011 · P0420 is VERY RARELY a failing cat. It is most commonly a failing oxygen sensor (front Subaru, rear any brand), vacuum leak, exhaust leak or what not. Search that code on the forums and you'll find plenty of info. Cats rarely fail without serious mechanical problems, I think your mechanic wants to give you an expensive repair bill. The P0420 code is a common issue that many Subaru Impreza owners experience. This subheading aims to provide a detailed explanation of what the code means and its implications for the vehicle. The P0420 code signifies a problem with the catalytic converter efficiency in the exhaust system of the Subaru Impreza.J. Jdave Discussion starter. 7 posts · Joined 2017. #11 · Sep 11, 2019. A code P0420 may mean that one or more of the following has happened: Leaded fuel was used where unleaded was called for (unlikely) A damaged or failed oxygen / O2 sensor Downstream oxygen sensor (HO2S) wiring damaged or connected improperly.The "official" fixes for a P0420 code are: replace the rear O2 sensor, replace the front O2 sensor and replace the cats. - Replacing the rear O2 sensor will accomplish nothing, IMHO - Replacing the front sensor is a good idea, since it is responsible for running the engine properly. Sadly, it probably won't solve the P0420 code issue.This code simply means that somewhere in the chain of events that controls the overall performance of the engine there is a problem and you have to find it. List of …Jan 5, 2009 · the most common problem for P0420 seems to be a bad O2 sensor. front O2 sensor needs to be OEM at about $100, rear O2 sensor can be parts store brand >$100. I also replaced my sticking EGR valve when i replace my front O2, dont know if that had anything to do with P0420. now it could also be a leak in the exhaust, replacing the gaskets seems to ... Subaru p0420, Nov 30, 2018 · The most common fix for P0420 in the Subaru Legacy is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Legacy into an exhaust shop for an (expensive) new catalytic converter, let’s ensure that’s what you need. Here’s a good P0420 diagnostic order for the Subaru Legacy: 1. Check for Other Codes. , This is a very common Subaru code. It ranges from seemingly "unfixable" (i.e., reflash the ECU to ignore it), catalytic converter replacement, rear O2 sensor, exhaust leak, all kinds of stuff. I wouldn't worry too much unless other symptoms/codes appear. My car throws a P0420 about every 1000-2000 miles (edit: and still gets high 20's average ... , Oct 19, 2015 · Every mechanic has seen intermittent P0420's that come back after months or a year, that's common. A P0420 due to an oil filter is unheard of. More than likely the P0420 was intermittent and was going to go out and come back at some point no matter what you did. H6 OBW VDC, H6 OB Sedan, Tribeca, Lifted XT6. traildogck. , The most common fix for P0420 in the Subaru BRZ is a new catalytic converter, followed by an O2 sensor replacement. Before taking your BRZ into an exhaust shop for an (expensive) new catalytic converter, let’s ensure that’s what you need. Here’s a good P0420 diagnostic order for the Subaru BRZ: 1. Check for Other Codes., Honestly, I think Subaru uses the P0420 to increase dealer repair traffic. If you're in a DIY mood, do a citrus clean on your cat. It's bolt-off, bolt-on. If you leave the rear O2 sensor in place, it will get a cleaning as well. If that doesn't do the trick, at least you've got the fasteners loosened for a replacement., The "official" fixes for a P0420 code are: replace the rear O2 sensor, replace the front O2 sensor and replace the cats. - Replacing the rear O2 sensor will accomplish nothing, IMHO - Replacing the front sensor is a good idea, since it is responsible for running the engine properly. Sadly, it probably won't solve the P0420 code issue., P0420 - Catalyst System Efficiency Below Threshold (Bank 1) P0031 - HO2S Heater Control Circuit Low (Bank 1 Sensor 1) ... but my view is the rear O2 sensor, which generates this code, is a poor after-thought by Subaru. The '$5 fix' reduces the sensitivity of the rear O2 sensor. It doesn't really 'fix' anything (except for the bleeping CEL light ;-), Most common causes for the P0420 code: failing oxygen sensor, exhaust leak, cat. failure. The first two are much more common and much easier to fix. If these don't fix it, then look at the cat. 2002 Outback wagon 3.0 L.L. Bean no more: " Mal ". 142,000 and counting. Mismatched cloth interior swap., Every mechanic has seen intermittent P0420's that come back after months or a year, that's common. A P0420 due to an oil filter is unheard of. More than likely the P0420 was intermittent and was going to go out and come back at some point no matter what you did. H6 OBW VDC, H6 OB Sedan, Tribeca, Lifted XT6. traildogck., May 23, 2011 · P0420 is VERY RARELY a failing cat. It is most commonly a failing oxygen sensor (front Subaru, rear any brand), vacuum leak, exhaust leak or what not. Search that code on the forums and you'll find plenty of info. Cats rarely fail without serious mechanical problems, I think your mechanic wants to give you an expensive repair bill. , Jan 10, 2012 · 63 posts · Joined 2011. #1 · Jan 10, 2012. I have a 2004 OBW and it keeps throwing the P0420 catalytic system below threshold code. The car is bone stock. It is drive by wire and has the California emissions on it. It's engine is a model EJ259 if I remember correct. I've tried using the anti-foulers, and even the electronic fixes in the rear ... , A while back the dreaded p0420 code came up, and recently I discovered a large leak just upstream of the REAR cat. The pipe is cracked along about a third of it's circumference. ... Welcome to the Subaru Outback Owners Forum, we have tons of information about your Subaru Outback, from a Subaru Outback Wiki to customer …, I have the dreaded P0420 code. It is intermittent. Base engine. No turbo. Just purchased this 2006 outback with 145k miles. Has a brand new cat and new front 02 sensor. ... Subaru runs a wideband O2 in the front. The 0-1v readout that most other cars have, does not apply to Subaru. The rear O2s are the standard 0-1v units., Eight hours a day is way too much at some Swedish companies. By clicking "TRY IT", I agree to receive newsletters and promotions from Money and its partners. I agree to Money's Ter..., It is rather random - the code will return in a day or months or a year. Simple procedure for a home DIY person or someone like me that sees this all the time: 1. make sure there are no leaks. 2. replace the rear O2 sensor. 3. replace the front O2 sensors. 4. install the $5 extenders and never think about it again., The gaming industry is just one example of an industry squeezed by regulation. South Africa’s uncertain digital regulatory environment may deter investors and tech entrepreneurs, d..., Mar 25, 2010 · One of my favorite threads for this is the $5 fix :wink: When you get the P0420 CEL code, the cause can be: A faulty or failing front O2 sensor (if your gas mileage has dropped off with hesitation, backfires & an overly sooty exhaust tip). An exhaust air leak ahead of the rear O2 sensor (rusted or cracked pipe). A failed CAT. , 63 posts · Joined 2011. #1 · Jan 10, 2012. I have a 2004 OBW and it keeps throwing the P0420 catalytic system below threshold code. The car is bone stock. It is drive by wire and has the California emissions on it. It's engine is a model EJ259 if I remember correct. I've tried using the anti-foulers, and even the electronic fixes in the rear ..., the most common problem for P0420 seems to be a bad O2 sensor. front O2 sensor needs to be OEM at about $100, rear O2 sensor can be parts store brand >$100. I also replaced my sticking EGR valve when i replace my front O2, dont know if that had anything to do with P0420. now it could also be a leak in the exhaust, replacing the …, I ran into a code that occurred 3 times now when driving on the freeway only at around 60-70 mph which was a P0420 code. I have been told by fellow Subaru enthusiasts in my area to replace the front O2 sensor, but read on this forum that it should be the rear sensor. On the 2011 LGT, the O2 sensors are close to each other so I really …, Welcome to the Subaru Outback Owners Forum, we have tons of information about your Subaru Outback, from a Subaru Outback Wiki to customer reviews. Show Less . Full Forum Listing. Explore Our Forums. Gen 5: 2015-2019 Problems & DIY Maintenance Gen 4: 2010-2014 Gen 6: 2020-present General Discussions., PO420 code. Thanks for taking the time to help. I have a 2004 Outback 2.5L automatic. J259. Code P0420. I've replaced the bank 1 sensor 1 with a Denzo brand. I've ran 2 different cleaners through the gas tank. I got the car with a blown head but had it fixed. I replaced the sensor after the head was fixed., P0420 is generally a universal code for Catalytic Converter limit below threshold or something along those lines. P0420 indicates a failing catalytic converter. ... A forum community dedicated to Subaru Impreza and STI owners and enthusiasts. Come join the discussion about performance, engine builds, exhaust, modifications, troubleshooting ..., "His was a life, full of gallantry, sacrifice, love for Nigeria and ever willing to die in order to keep it one." A good number of Nigerians have been through life under military r..., JENNISON GROWTH EQUITY FUND 6- Performance charts including intraday, historical charts and prices and keydata. Indices Commodities Currencies Stocks, I'm thinking it definately needs a tune up and some other minor maintenance. An issue I had planned on tackling as things started settling down for me here soon. However, yesterday as I was driving, the CEL came on in conjunction w/ the CRUISE caution light. Went to autozone, and got the P0420 code., GM CEO Mary Barra sees the automaker selling personal autonomous vehicles by the end of the decade by leveraging technology from its self-driving subsidiary Cruise, according to co..., That's one of Subaru's plans to make you fix your car instead of ignoring the code. In my experience the P0420 code has always been fixed (4 times on three different cars, and the second time on one car was the other bank on a 3.6R) by replacing the downstream O2 sensor. Did you replace it with a good brand-name sensor or whatever …, This is a very common Subaru code. It ranges from seemingly "unfixable" (i.e., reflash the ECU to ignore it), catalytic converter replacement, rear O2 sensor, exhaust leak, all kinds of stuff. I wouldn't worry too much unless other symptoms/codes appear. My car throws a P0420 about every 1000-2000 miles (edit: and still gets high 20's average ..., P0420 is generally a universal code for Catalytic Converter limit below threshold or something along those lines. P0420 indicates a failing catalytic converter. ... A forum community dedicated to Subaru Impreza and STI owners and enthusiasts. Come join the discussion about performance, engine builds, exhaust, modifications, troubleshooting ..., Air can and does enter cracks or small holes in the exhaust. A system in good shape does not have measurable pressure in it. The exhaust flowing through the pipe can draw ambient air in through openings. A partially blocked converter won't necessarily throw a P0420 code if it is still working as a catalyst., 104 posts · Joined 2008. #2 · Oct 3, 2011. I as well have been dealing with the P0420 and a local subie dealer out here mentioned basically to clear the code and see how long it takes for it to come back up. Meanwhile, run fuel cleaner through the system to clear up the injectors and the 02 sensors. You said your putting the anti-foulers on ..., Even slight variations in the air/fuel mixture will cause the converter temperature to rise significantly. The “Catalytic Converter Efficiency” Diagnostic Trouble Codes (DTCs) P0420 and P0430, are among the top 10 DTCs technicians face. And while the description might imply a failed converter, odds are the ultimate fault lies somewhere …