Subaru p0420 - plain OM. 21404 posts · Joined 2006. #2 · Jan 2, 2013. There's no shortage of posts and threads about P0420 both here and in other forums. It seems the code could be referring to a problem with a catalytic converter, a sensor, or something totally remote. Perhaps the most interesting and enlightening demonstration of this is cardoc's http ...

 
This week Dana is working on correcting the issue of Code P0420, a Bad Catalytic Converter. We started this project off with a Dorman aftermarket catalytic c.... Land for sale in upper peninsula michigan

Subaru code P0420 refers to a diagnostic trouble code that indicates an issue with the catalytic converter efficiency in the vehicle’s exhaust system. This code …In 2021, I had a lot of fun working to track down a P0420 code. As a result of this, I found several other issues with my 2016 WRX (manual transmission), and fixed them. The following have been successfully done: Full engine rebuild (new pistons, bearings, gaskets.... the works) - No mechanical issues. No fluid leaks of any kind.In this video I am working on a 2014 Subaru Outback with a 2.5 and CVT. We have done quite a bit of work to this car to solve an ongoing P0420 code. Make su...2005 outback 3.0, p0420 bank one sensor 2 New Desno O2 sensors, new cat ... Although it refers to Bank 1, where there's a separate cat for each bank Subaru uses P0420 for efficiency below threshold for either bank. There's no code for CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD for Bank 2, even though this is a …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 light" gets its n...Visit me at: http://www.ericthecarguy.com/O2 Sensor Video: https://www.youtube.com/watch?v=NIzcztO-CCsDiscussion about this video: http://www.ericthecarguy...Jan 1, 2014 · There's some good information from that post onward. The gist of these messages and threads is this: to deal with a P0420 code on 2005+ vehicles, the ECU should be remapped to exclude this code, rather then using the $5 fix. The reasoning is that the rear O2 sensor is actually used to manage the engine, at least a little bit, rather than just ... The connection to your P0420 isn't an obvious one (at least to me). Typically the problems associated with a bad PCV valve is that you end up with a mildly pressurized crankcase rather than one below atmosphere, and you push oil out from your valve cover gaskets or spark plug tubes. '19 Forester Premium, '18 Forester Limited, '15 Toyota …In 2021, I had a lot of fun working to track down a P0420 code. As a result of this, I found several other issues with my 2016 WRX (manual transmission), and fixed them. The following have been successfully done: Full engine rebuild (new pistons, bearings, gaskets.... the works) - No mechanical issues. No fluid leaks of any kind.2001 OB H6 infamous p0420 help deciphering it. I have an ultragauge and for about the last year would get a random pending check engine code p0420, this is only like 4 or 5 times in an 18 month period. For those unfamiliar with the ultragauge a pending code is a pre code not enough to throw an official check engine but its getting close.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 ... Tech Notes. As the code description implies, the P0420 code means that the vehicle's Engine Control Module (ECM) has detected that the Three-way Catalyst Converter is not working properly (it is not as efficient as the factory expects). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases, the Three-way Catalyst ...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-...Dec 2, 2022 · 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 car is a 2005 Outback 3.0R with 130000 Km on it. That minor rant aside, the CEL popped up recently (following my wife running out of gas) and the code was a P0420 catalytic inefficiency. Did my reading on this forum and did the following: - Checked exhaust for leaks. - Replaced PCV. - Replaced air filter.Chapter/Region: NESIC. Location: Lake George , New York. Vehicle: 2021 WRX BASE. Pure Red. Code P0420 and P0137 after Invidia Catted J pipe install on 2021 wrx. So , last month I installed my Invidia catted j pipe and with it the Cobb stage 2+ big sf intake on my 2021 WRX 6-MT . I also have a remark mid pipe and axle back muffler …P0420 Subaru Catalyst System Efficiency Below Threshold Bank 1. As the code description implies the P0421 Subaru 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). Replacing the oxygen (O2) sensors may sometimes fix the ...How to diagnose code P0420 on a Subaru Impreza. Typically, you'll find out about P0420 because your malfunction indicator lamp or "check engine light" turned on & you or a mechanic diagnosed the problem with an OBD II code scanner like this one from Bluedriver. You may experience a very slight reduction in engine power from reduced exhaust flow ...B. bdubbs84 Discussion starter. 13 posts · Joined 2008. #7 · Oct 20, 2008 (Edited) Well, I got rid of the P0420 catalyst code, but now I have two new codes. One is P0440 (Evap. Emission Control System Malfunction) and the other is P0136 (O2 Sensor Circuit Malfunction, Bank 1 Sensor 2). I already have the O2 sensor spacer in place.Visit me at: http://www.ericthecarguy.com/O2 Sensor Video: https://www.youtube.com/watch?v=NIzcztO-CCsDiscussion about this video: http://www.ericthecarguy...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).Subaru Service Bulletins are intended for use by professional technicians ONLY. They ... DTC P0420 (Catalyst System Efficiency Below Threshold Bank 1) is detected by the Engine Control Module (ECM). If DTC P0420 is found to be …2009 Subaru Outback P0420. It was diving awesome with no sign of issue when I got a CEL and my cruise and stability control lights came on and the systems disabled. This happened on the way home from purchasing the car. No sign of issues on my test drive Tested the code and it showed P0420.The most common fix for P0420 in the Subaru Tribeca is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Tribeca 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 Tribeca: 1.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 …In this video I am working on a 2014 Subaru Outback with a 2.5 and CVT. We have done quite a bit of work to this car to solve an ongoing P0420 code. Make su...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.Generally P0420 code can be set by exhaust leaks, bad O2 sensor or a bad cat. P0420 definately seems to be a common occurrance with some Subaru's. PZEV might have more. and I was reading those PZEV 2005-2009 cars also race their engines on first cold up, to heat the cats up fast and to stop the stink. (like H6 ones do).If the code is happening on a later model Subaru (2015 - present) the chances are it's a bad catalytic converter, otherwise a newer model would throw a specific code for the oxygen sensor if it was the culprit. P0420 Code in Toyota. If you have code P0420 in Toyota models, it's usually due to a faulty catalytic converter.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 ...The CEL would turn on and off occasionally so I changed the Wires, Plugs and coil pack and went ahead and did the 2 - O2 Sensors. Now over time I have earned 2 additional codes for my efforts. I have all three, (P0301, (Cylinder 1 Misfire Detected), P0303, (Cylinder 3 Misfire Detected), & P0420, (Catalyst System Efficiency Below …If you’re an avid DIYer and a car enthusiast, you may have come across the dreaded “Code P0420” at some point. This diagnostic trouble code is related to your vehicle’s catalytic c...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 …Nov 30, 2018 · The most common fix for P0420 in the Subaru Forester is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Forester 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 Forester: 1. Check for Other Codes. Here are the most common causes of P0420 in the Subaru Impreza: Likely Causes. Bad catalytic converter; Bad O2 sensor; Other Causes. Exhaust leak; O2 …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. If you are a car owner, it is likely that you have encountered the dreaded check engine light at some point. One of the most common trouble codes that many drivers come across is c...double check battery connections. catch-up on any any postponed maintenance. the P0420 often is due to something unrelated to the cat conv so, that should be the last thing you suspect. Exhaust leaks, vacuum leaks, weak spark.... Time Flies Like an Arrow, Fruit Flies Like a Banana! Hans747. Like.There's some good information from that post onward. The gist of these messages and threads is this: to deal with a P0420 code on 2005+ vehicles, the ECU should be remapped to exclude this code, rather then using the $5 fix. The reasoning is that the rear O2 sensor is actually used to manage the engine, at least a little bit, rather than just ...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.Hi all, I've been chasing a P0420 code on my base 2007 outback (to prevent the CEL from coming on so my cruise will work). Check engine light first came on with P0420 after about a hundred miles. ... Our converter manifold is compatible with the2005-2010 Subaru and 2006 Saab 9-2X 2.5L, helpful in upgrading the exhaust system to …59 posts · Joined 2015. #1 · May 23, 2020. I'd greatly appreciate some help troubleshooting a P0420 code on my '07 OB. I've reviewed many posts on this, including the P0420 Diagnosis post on the Problems and Maintenance forum, but I'm not understanding some of the basics. Many of the posts refer to checking for exhaust leaks.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...Individual retirement accounts offer significant tax benefits to help boost retirement savings. While you may be tempted to withdraw money from your account before you retire, trea...JENNISON GROWTH EQUITY FUND 6- Performance charts including intraday, historical charts and prices and keydata. Indices Commodities Currencies Stocks 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. The P0420 is a finicky code. There is a range of "acceptable" parameters that Subaru has set. If the O2 sensor sees a value that is outside of that range, even for just a fraction of a second, you get the P0420. Adding the extension doesn't stop the O2 sensor from working, it just doesn't get the immediate read, but more of a mixed read.The trolley problem looks to explore the concept of human morality and a philosophical view of consequentialism. Learn about the trolley problem. Advertisement It's a lovely day ou...P0420 Code Chasing - Graph of O2 Sensor. Hi all, I've been chasing a P0420 code on my base 2007 outback (to prevent the CEL from coming on so my cruise will work). Check engine light first came on with P0420 after about a hundred miles. I reset the code, and after about 60 miles I saw the code "pending" again though it wasn't confirmed and no ...The Insider Trading Activity of Walbrecht John on Markets Insider. Indices Commodities Currencies StocksB. bluewagon Discussion starter. 83 posts · Joined 2015. #1 · Mar 4, 2016. Hey guys, Like to get your thoughts on this. CEL went off with a P0420 code. FreeSSM description is "Catalyst System Efficiency Below Threshold:". From what I've gathered this kind of CEL could be fault of either the front o2, back o2 sensor or the catalytic converter.both. p0420 is a cat efficiency code. this code is specifically triggered by the rear 02 sensor seeing that the cat is not doing its job. this code is the most common exhaust code one can get. we see it all the time. 2 things can make the sensor throw the code. either the sensor is borked, which means you buy a new sensor, or the sensor is …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 P0420 is a finicky code. There is a range of "acceptable" parameters that Subaru has set. If the O2 sensor sees a value that is outside of that range, even for just a fraction of a second, you get the P0420. Adding the extension doesn't stop the O2 sensor from working, it just doesn't get the immediate read, but more of a mixed read.2008 Subaru Outback 2.5L with p0420. Problem: MIL Lamp on (P0420) Diagnosing: The data on the oxygen sensor look unusual so he decided to change both of them, clear the codes and return the car to the customer. The car is back after a few days with the same code. The technician replaced the valve cover gaskets and catalytic converter.The P0420 code signals a low catalyst system efficiency. This code suggests that the oxygen levels are below the desired threshold (Bank 1), which most often results from problems with your car ...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 ...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 ...Using my cheap scanner I have a P0420 code "Catalyst System Efficiency below threshold". Some info I found pointed to these sensors: Mass Air Flow. Manifold Absolute Pressure. Engine Coolant Temperature. Air Fuel (upstream O2 Sensor) O2 (downstream O2 Sensor) Other info was to change the spark plugs, it is about time.Nov 19, 2017 · Causing bad readings which throws a code telling you that you need a new cat or O2 sensor. Start up front and move your way to the exhaust. Hey Tyler, air filter is stock, I haven’t changed it yet, I’ll check right when I get off work. 11-16-2017, 10:15 AM. # 6. gn4rwhals vbmenu_register ("postmenu_45422896", true); P0420, catalytic converter, and rattle noise. Just purchased a 2002 Outback 2.5L, 4 cylinder, 4 Door sedan with 140,000 miles. After a couple of weeks the check engine light came on and the P0420 code was the diagnosis. After reading other post it appears I should replace the 02 sensors and see if that fixes the problem.45837 posts · Joined 2007. #2 · May 17, 2020. @Jaime ochoa welcome to the forum from Oregon! The P0420 CEL code is from the rear O2 sensor, but that doesn't mean the sensor is bad. The rear O2 sensor is monitoring for excess 02 in the exhaust flow, so the fault could be something upstream... even a pinhole leak in the exhaust pipe?Using my cheap scanner I have a P0420 code "Catalyst System Efficiency below threshold". Some info I found pointed to these sensors: Mass Air Flow. Manifold Absolute Pressure. Engine Coolant Temperature. Air Fuel (upstream O2 Sensor) O2 (downstream O2 Sensor) Other info was to change the spark plugs, it is about time.Check Engine Light and P0420 and P0430 Codes. So, your Check Engine light is on, and you’ve got either a P0420 or P0430 code, on your OBD-II scanner. This “Catalyst system efficiency below threshold” code is triggered when your car’s computer (the powertrain or engine control module (PCM or ECM)) detects a catalytic converter …8 posts · Joined 2019. #1 · Aug 25, 2019. Hey guys I just picked up my 04 Forester a few weeks ago as my first car and I love the car so much already but I recently just had my Check Engine Light pop up. Ran the code and got " P0420 - Catalyst System Efficiency Below Threshold Bank 1". I did some research and I'm pretty positive one of my o2 ...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 ... 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.JENNISON GROWTH EQUITY FUND 6- Performance charts including intraday, historical charts and prices and keydata. Indices Commodities Currencies StocksA 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 …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.2012 Forester 2.5X Manual 5spd - 142,309 miles. I bought the car in July 2021 with 116,000 miles. About 8/10 months ago or so, a P0420 code popped up, I did nothing about it for awhile since the car seemed to be running fine. Then a few months ago the car stalled as I was exiting the highway approaching the stop light at the end of the …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 ... If you are a car owner, it is likely that you have encountered the dreaded check engine light at some point. One of the most common trouble codes that many drivers come across is c...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.Feb 20, 2015 · 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. Exhaust Leaks. An exhaust leak can cause the P0420 code by allowing excess oxygen into the exhaust stream and disrupting the catalytic converter's ability to reduce emissions. Malfunctioning EGR …p0420 catalyst efficiency low bank 1. I have had my check engine light come on and go off several times in the past 9 months, but the last time it came on it did not go off, so I took it to aplace to find out what is the problem, so he hooks it uo to this snap on computer and read the code as p0420 catalyst efficiency bank 1, and he rests it.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.M. mudd123 Discussion starter. 15 posts · Joined 2014. #1 · Feb 5, 2015. My 2003 OB w/ 2.5 135k developed P0420 code back in August. I have been playing around with it for awhile trying to figure it out. Here is the background on what took place: The CEL came on on a HOT and HUMID day while going about 60 mph, and about 1/8 of a tank …The most common fix for P0420 in the Subaru Baja is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Baja 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 Baja: 1. Check for Other Codes.Desferal (Injectable) received an overall rating of 7 out of 10 stars from 1 reviews. See what others have said about Desferal (Injectable), including the effectiveness, ease of us...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 …Subaru Liberty P0420 OBDII Code Defined. P0420 is a OBDII trouble code. The code technically stands for: Catalyst System Efficiency Below Threshold. Your Liberty has at least two oxygen sensors, one before and after the catalytic converter. Among the many jobs that oxygen sensors have is they have to measure the emissions levels …P0420 is a sign the o2 and air fuel sensors are functioning and they are monitoring the catalyst properly. The EASIEST way to tell if a catalyst is worn is the smell of raw fuel from the exhaust. Confirmation is difficult without a graphing scan tool, I graph the front o2 to the back and watch the rear o2 sensors activity in comparison to the ...

/r/WRX is a place for Subaru fanatics to show off their rides, discuss modifications, mechanical issues, industry news, and more. ... P0420 and P0172. Was able to find out the Big SF was the cause of the P0172. I’ve heard of faulty MAF extensions and filters and I’m working with Cobb on the intake currently (was running the correct OTS tune. 30x50 steel building

subaru p0420

Looking for a Subaru dealer? With over 20 dealerships across the country, you can discover one near you and find the model that fits perfectly into your world.Tel: 01293 429800. Subaru UK's range of all-wheel drive SUV and family cars including the brand new Solterra and XV models. Discover the Subaru that fits into your world.There are several potential causes for Subaru code P0420, including a faulty catalytic converter, oxygen sensor malfunction, exhaust leaks, engine misfires, or issues with the fuel system. It is important to diagnose the specific cause accurately to determine the appropriate course of action.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 …Apr 9, 2017 · If you've cleaned your MAP, then all that's left is the rear O2 sensor and the cat itself. Dealers change rear O2 sensors . . . mostly because that's one of the few pieces left in the puzzle. Then comes the cat . . . chi-ching! Honestly, I think Subaru uses the P0420 to increase dealer repair traffic. 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. 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.Code P0420 Description. The Engine Control Module (ECM) uses sensors mounted in front of and behind the Three-Way Catalytic Converter (TWC) to monitor its efficiency. The first sensor, the air-fuel ratio sensor, sends pre-catalyst information to the ECM. The second sensor, the heated oxygen sensor, sends post-catalyst information to the ECM.The trolley problem looks to explore the concept of human morality and a philosophical view of consequentialism. Learn about the trolley problem. Advertisement It's a lovely day ou...The codes are: P0420: Catalyst System Efficiency Below Threshold (bank 1) P0422: EVAP Control System Leak Detected (Small Leak) I am now in a new area and went to a mechanic who wasn't familiar with my vehicle history. I explained my situation and mentioned to Rear O2 sensor issue of the past. This mechanic read the codes and said …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 ....

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