Here’s how you can troubleshoot and potentially resolve the P0420 code in your Subaru Forester: Inspect the Catalytic Converter: Check for any physical damage or signs of …So heres my issue, I have a 2004 Subaru forester X with around 138k miles on it, couple months ago my engine went out so I swapped a rebuilt ej25. Engine runs fine but its idles fairly high at time around 1k-2k rpms. Originally I got a code for the rear o2 sensor. Replaced it but problem persisted and I started getting a p0420 code.But it's declined, and runs really crappy and rough all the time now. So I took it to my mechanic buddy who replaced the trans (trustworthy guy), and his scanner pulled P0304, P0302, P0301, and P0420 codes... so all of the cylinders are misfiring except #3, and of course the catalytic code, which could be a result of the cylinders misfiring, or ...See Also: P0420 Subaru Forester . Subaru Forester P0430 Code Symptoms. There aren't usually any drivability issues associated with P0430. For most people the first sign that anything is wrong at all is the service engine soon light coming on. ... Service Engine Light- Often, this is the only symptom of the Subaru Forester P0430 code ...A P0420 CEL code comes from the rear O2 sensor, usually meaning there's too much O2 in the exhaust. The usual suspect is a leak in the exhaust, or an overly rich condition. ... We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. Show Less .Subaru’s Lineartronic CVT design uses a chain rather than a cable to join the two pulleys of the CVT system as in most other CVT designs.Hi guys.. I too have the same code P0420 on my ‘01 Forester L, 120K miles. ... We’re the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. Show Less . Full Forum Listing.Cats do fail on a regular basis, odd fuel trim/missfire problems destroy the cat, or pinhole exhaust leaks set off the P0420 code. Not so much on Subarus. I see a lot of subaru cat's replaced because of the P0420 code, often with inferior aftermarket cats, and 10 months later the light is back on and the customer is out $600 or more.VSurfn. 1329 posts · Joined 2014. #2 · Jul 22, 2018 (Edited) P0420 code stands for "Catalyst System Efficiency Below Threshold (Bank 1).". When you receive a P0420 code it means your catalytic converter is not operating at maximum efficiency. Usually this means your catalytic converter needs to be replaced and/or your O2 (oxygen) sensors.P0420 and stalling issue. Shortly after buying my '07 Limited, the CEL came on. I had an appointment at the dealership for an oil change & they did not tell me the code number, only "that code usually means you need a new cat converter.". They cleared the code, no estimate for the converter.P0420 - Will new DP fix it? ('03-'05) Jump to Latest Follow 21 - 24 of 24 Posts. 1 2. Buddur · Registered. 2006 Forester Joined Feb 28, 2007 · 695 Posts #21 · Nov 29, 2015 (Edited ... Subaru Forester Owners Forum. 2.6M posts 191.1K membersJul 18, 2017 · Also, P0420 can be the cat, but it can be a number of other things including rear O2 sensor, intake/exhaust leak messing with the air fuel ratio, spark plugs, fuel ...He has many many used foresters for sale and probably has a rebuilt engine ready to go or he can do yours. He is comparably cheap. Ph-717-426-4142. Tell him Al Conrad sent you. The other guy is every bit as good but a bit more expensive and probably doesn't have a rebuilt. He is Subaguru 717-786-2304.2002 Subaru Forester S P0420 Own a 2002 Forester S (purchased late 2001), 127,000+ miles, mostly city driving the past 6 years or so. Would like to keep the car for my teenage son, who will start driving this summer. Have always used mid-grade gas in the car, and am religious about oil changes, etc.CLEAN Your CAT - Fix stubborn P0420 Here's what I did: On 2005 Forester XT with P0420, 1. Removed downpipe/catalytic converters. 2. Separated into upper Cat and lower Cat. 3. In a 5-gallon bucket, mixed 4 gallons water, 10 oz. Citric acid and 7 oz Oxalic acid. (Purchased on Amazon - $20) 4. Soaked main Cat in acid overnght, rinsed …Hi guys, just after a bit of advice on my foz. It was recently mapped and Duncan noticed it was running rich, but was unable to lean it out without causing running issues. The only symptoms are sooty exhaust and high fuel consumption (27 mpg even taking it very easy on the motorway), and a slight hesitation when accelerating hard from 3000rpm ...May 13, 2023 · 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.Two weeks ago I had to have the front O2 sensor replaced on my 2000 Forester. Just last night I got a CEL and went to Auto Zone to check the code. It was …2007 - O2 converter (P0420) / head gasket leak? Hi my high mileage (443K km) Forester has been throwing a check engine code for a while now. Got it read and it was P0420 - Catalyst System Efficiency below Threshold, Bank 1. My mechanic just called and 1) noted the head gasket leak is much worse than previous); 2) cylinder 3 is misfiring; and 3 ...The catalytic converter, as you might know, is a government-mandated device in the Subaru Forester's engine that converts toxic gases & pollutants into less-toxic chemicals by means of extreme heat & multiple stages of chemical processing.. If the catalytic converter isn't working like it should, your engine will let off more pollution than …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...Fits Forester (2004 - 2005) EGR Valve Temperature Sensor A failed EGR Valve Temperature Sensor will often have no noticeable symptoms beyond a check engine light, but it does cause your Subaru Forester to operate inefficiently and produce higher emissions. Our technicians have access to manufacturer-approved repair processes and Subaru genuine ...Here are the most common causes of P0455. How your Forester's EVAP system works will depend on the model year and engine type.. Evap System Hose- The EVAP hose carries fuel vapor from the fuel tank to the intake manifold can begin to leak.This will cause the P0455 code. Look for either a tear or in the hose.Back in May 2020, I sent my Forester XT to the dealership to take care of the recall for the insufficient tightening torque of EPF nuts. The invoice states that they "INSPECTED EPF AND FOUND MANIFOLD LEAKING, INSTALLED NEW MANIFOLD AS PER RECALL, AND INSPECTED FOR LEAKS, TOPPED OFF ENGINE OIL AND COOLANT.'' Cool - I'm glad I got that out of the ...A P0420 CEL code comes from the rear O2 sensor, ... We’re the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru …1. Visit autoshop and have them repair it by cleaning and/or replacing the parts. Total estimated cost is $900+. This will only reset the imaginary timer for it to re-occur again in the future. 2. Buy Accessport ( link) ~$400 used/$600 new and TGV delete kit ( link) $68.Pine Hollow Auto Diagnostics. 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...The P0420 code is a diagnostic trouble code (DTC) related to the efficiency of the catalytic converter. This code appears when the vehicle's engine control module (ECM) detects that the catalytic converter is not functioning as efficiently as it should, based on the readings from the oxygen sensors located before and after the converter.P0420 is for Catalytic converter .... yea it is possable that a bad rear o2 sensor could cause that code , ... We’re the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. Show Less . Full Forum Listing.What Does Code P0420 Mean? OBD II fault code P0420 is a generic code that is defined as "Catalyst System Efficiency Below Threshold (Bank 1)", and is set when the PCM (Powertrain Control Module) detects a condition that indicates that the catalytic converter on Bank 1 is operating below the minimum allowable efficiency threshold. Note that on engines with two banks of cylinders, "Bank 1 ...P0420 Subaru - Código DTC de falla OBD2. P0014 Subaru - Código DTC de falla OBD2. Deja una respuesta Cancelar la respuesta. Tu dirección de correo electrónico no será publicada. Los campos obligatorios están marcados con * Guarda mi nombre, correo electrónico y web en este navegador para la próxima vez que comente.Cleaned fuel injectors, put new filters and o-rings in. Did a valve lash adjustment and checked compression and everything at the shop that did the head and block work. I just did a basic stage 1 rebuild, its a NA ej251. The car was running fine after the valve lash adjustment but then I had the P0420 code come back shortly after that.Subaru / Forester / 2000 / p0420; P0420. 2000 Subaru Forester. Asked by dw782 in San Francisco, CA on . December 19, 2009. I get a po420 code, and also my gas mileage is has gone noticeably down. I have a scanner and reset the code twice, and noticed in live data the pre-cat sensor reads consistently at 1.5v or above and the post-cat sensor is ...P0420. I have a 2004 Legacy 2.5 California spec (3 cats, 5 O2 sensors) with a recurring p0420 pending code on bank 1 that keeps popping up on my blue driver for the past 2000 miles. The cats were replaced under warranty about 8-9 years, 100,000 miles ago. The Oxygen sensors are all original, so they have 167,000 miles on them.Paid $90 for useless test. I bought front sensor off Amazon for less than $100. Installed sensor, reset code. On the second highway trip the cel trips code 0420. I rerun subaru test procedure. Results show sensors fine, bad cat. I replace the rear sensor so that when I take the car back to Subaru they should have no option but to replace the cat.As long as I drive my '09 forester X limited at this altitude all is well, car runs fine, plenty of power, good mileage, etc. If I drive the car to Colorado Springs at about 6,500 ft., It almost always sets the P 0420 Catalytic insufficiency code.The OBD code p0420 is a summary code indicating that something was not quite right with the catalytic converter output at some point in the past. The code is not a basis for action except to investigate further. ... We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability ...P0420 is for Catalytic converter .... yea it is possable that a bad rear o2 sensor could cause that code , ... We’re the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. Show Less . Full Forum Listing.45853 posts · Joined 2007. #7 · Sep 2, 2022. @SueBrew on your 2001, the rear, downstream O2 sensor function is to monitor the efficiency of the CAT. It's not used by the ECM for engine management, just to give you a P0420 CEL code if too much O2 is detected in the exhaust flow.. Your only issue is that P0420 CEL code, no other CEL codes.The future of fully autonomous robots may be built by a company that is laser scanning the boreal forests of Finland with drones. Helsinki-based Sharper Shape is already bringing a...P0420 is the front cat. It's needs to be replaced....and it'll be under warranty.. FREE. TrailAngel 2010 2.5X 5MT. Save Share. Like. J. james gais Discussion starter 13 posts ... Subaru Forester Owners Forum. 2.6M posts 191.2K members Since 2006 We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester ...The P0420 CEL code + reduced gas mileage would point me upstream. The rear O2 sensor is good, as it's telling you there too much O2 in the exhaust... as in, you're running too rich. So rich that the CAT can't reduce the O2 levels. That would also explain the poor gas mileage.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 …2010 X Premium, 130000 miles. About 300 miles ago the CEL came on . After scanning the system I had a P0420 'permanent " stored code. I replaced both O2 sensors with new Denso units. The CEL went out and all seemed good. Now 300 miles later I have 2 codes, P0420 and P0031. Both are listed as confirmed and a P0420 is also listed as …2.5x_sleeper. 45859 posts · Joined 2007. #5 · May 29, 2023. @Highest_Harvest looks like low end is around $300, upward to over $500 on RockAuto, as the front CAT & headers are one piece. Normally a P0420 CEL code is caused by too much O2 in the exhaust flow from the engine running too rich.2024 Subaru Forester 2024 Subaru Outback 2024 Subaru Ascent 2024 Subaru Impreza Shop By Model. Pre-Owned Inventory Pre-Owned Inventory. All Used Inventory ... P0420: Inefficient Catalytic Converter(s), Defective Front or Rear Oxygen Sensor(s), Misfiring engines: P0430:Oct 5, 2021 · Bought my 2014 Forester 2.5L in July; 3 weeks later, engine light came on, P0420; Finally got it looked at last week, they found a vacuum leak, fixed it, and said it was good to go; Two days later, engine light came back on, took it back to the shop, and they said it was the front cat and it needed to be replaced2006 - P0420 code and O2 sensor value at 2,8V? ('06-'08) Jump to Latest Follow 630 views 2 replies 2 participants last post by syl20.m ...633. 176K views 8 years ago. This low kilometer Subaru Impreza flags a P0420 Catalyst efficiency fault code very quickly. The rear O2 sensor would behave …32 posts · Joined 2012. #1 · Jul 31, 2012. These 2 lights (ABS/Traction Control) have been coming on together recently. (The traction control won't turn off/on if pressed). They come on and seem to shut off randomly. They usually stay on until I restart the car. I researched this problem for foresters and found this code: Code 71 - steering ...Drop the splash guard and pull the plastic tabs closest to the fender well from under the car. You're going to need a 22mm wrench to remove the sensors, and the wiring harness is hard AF to remove. You may have to pull the large metal brace down, it's just 2 12mm bolts (one front one rear) holding it up. Then you'll have full access to everything.Subaru Forester P1604 OBD-II Diagnostic Powertrain (P) Trouble Code Information Page. Reason for Subaru Forester P1604 and find the solution for the code Subaru Forester P1604 , we'll give to how to fix Subaru Forester P1604 trouble code problem. p1604.enginetroublecode.comSeveral factors can trigger the P0420 code in a Subaru Forester. Understanding these causes can help in diagnosing and resolving the issue effectively. In detail: Some common causes include a failing or damaged catalytic converter, oxygen sensor issues, exhaust leaks, engine misfires, or even a faulty fuel system.2005 Forester bought last year for my son who is in school about 3 hours away. Chasing a re-occurring P0420 code, I have replaced or checked the following: PCV valve – OEM – original valve was not clogged Plugs – NKG – removed plugs looked good, no evidence of oil or unusual wear. Wires- NKG Front and Rear 02 sensors – DensoPlease Like, Comment, and Share. Be sure to subscribe for future videos. Don't forget to hit the bell icon for notifications. YouTube has changed what they s...Hey guys, I recently have been having issues with my 2019 subaru. I went to go get the diagnostic code and it came out p0420. Apparently it's the catalytic converter, but I feel like it's to new of a car to have issues with it.2002 subaru forester with a p0420 code. bank 1. what needs to be done? Unfortunately, the P0420 is a fairly straight forward code, and a fairly common problem. This code points to a failing Catalytic Converter. The Oxygen Sensors measure the amount of emissions in the exhaust going into, and then out of the converter.Apr 10, 2011 · Hey all, new to the fourm. I have a 03 2.5 xs with about 135k. The cel fires two identical p0420 codes about once a week. I have done a visual inspection and everything seems to be in order. i have a actron super auto scanner and use it under global obdii.HELP: Code P0420. My 2009 forester has the "cruise" light blinking and a solid traction control off and check engine light. I got the diagnostics ran and it came out with "P0420: catalyst system efficiency below threshold bank 1". This happened to me last year but ignored the symptoms for about a month and then had to get it taken in ...I have a 2011 2.5x (65k miles) and the CEL light came on after filling up with gas a few weeks ago. I checked to make sure gas cap was tight and CEL was still on. I had the codes read and it showed P0171 & P0420. I reset the codes to see if it might have just been the gas cap, but CEL came back on. I've noticed a decrease in gas efficiency ...NO, P0420 code started BEFORE the exhaust work, has been CEL since I got the car. The P2096 code started some time after the $5 fix AND the exhaust work. ... We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. Show Less .32 posts · Joined 2015. #11 · Dec 24, 2015 (Edited) P0420 - need some specific help. From what I understand, that rear o2 sensor waveform in the third picture is classic sign of a bad cat. It's likely that waveform that is triggering the code. The others look more stable, unless the scale is off. But the rear still mirrors the front.Just under three hours from San Francisco, 730 acres of redwood forest will open to the public for the very first time as the Harold Richardson Redwoods Reserve in 2021. Just under...This Service Information Bulletin announces diagnostic service procedures to be followed when DTC P0420 (Catalyst System Eficiency Below Threshold Bank 1) is detected by the Engine Control Module (ECM). If DTC P0420 is found to be stored in the ECM, follow the diagnostic procedures outlined below.The only way a P0420 is going to reflect on a stall is if you have a plugged catalytic converter. More likely a misfire is occurring as result of the stall enabling the P0420 code. ... We’re the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru ...32 posts · Joined 2015. #11 · Dec 24, 2015 (Edited) P0420 - need some specific help. From what I understand, that rear o2 sensor waveform in the third picture is classic sign of a bad cat. It's likely that waveform that is triggering the code. The others look more stable, unless the scale is off. But the rear still mirrors the front.If you want the P0420 CEL electrical fix, take a look at this link: O2 Foolers, The Economical, Electrical Way!! ... We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. Show Less . Full Forum Listing.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.Dec 26, 2009 · 2.5x_sleeper. 45860 posts · Joined 2007. #5 · Dec 26, 2009. My guess is a failing front O2 sensor, causing an over rich condition. This would give you the gas smell & would overwhelm the CAT. The rear O2 sensor, which monitors the CAT, would give you the P0420 CEL code. Sounds like what happen in my '03. :wink:P0420 . Today my 2015 forester threw a P0420 code; I am in the Kansas City area and we just had a gnarly week long winter storm (8+ inches of snow, -10 temps and -30 wind chills). ... Related Subaru Forester Subaru Subaru Cars and Motor Vehicles forward back. r/Subaru_Outback. r/Subaru_Outback. Subaru_Outback is a place for owners and ...Troubleshooting issues (P0420 surging/poor idle) Update: I'm an idiot! I just recently purchased a 2000 N/A forester 5spd with 240k miles less than two weeks ago. Without going through the whole story I'll just post the facts and then ask my question. PO said head gasket was replaced, no visible signs of leaks can be seen.P0420 - Catalyst System Efficiency Below Threshold (Bank 1) P0031 - HO2S Heater Control Circuit Low (Bank 1 Sensor 1) P0134 - O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1) The last 2 CEL codes are pointing to a defective front O2 sensor or the wiring to the front O2 sensor. The most recent was replacing the front O2 sensor on the cat.31 posts · Joined 2006. #1 · Feb 19, 2008. I originally posted a question regarding OBD2 code P0133, but now I have additional info that I could use help on. Ok...there's now been one instance of a P0420 code, catalytic system efficiency below threshold (bank 1), to go along with the intermittent P0133 codes I've been getting.Catalytic Converter fits Subaru Forester Impreza Legacy Outback 2006 - 2010 2.5L | eBay Our converter manifold is compatible with the2005-2010 Subaru and 2006 Saab 9-2X 2.5L, helpful in upgrading the exhaust system to improve vehicle performance. ... Car is not overly loud or anything. Doubt that really has anything to with the p0420 code as (I ...The P0420 is set because the two O2 sensors are showing the same or close to the same readings. ... We’re the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. Show Less .I came across this thread doing research on a potential bug in the VDCCM module on my 2008 Subaru Outback. I think the VDCCM module is raising trouble code C0042 by mistake when the CAN bus is interrupted. It should be raising C0044 on cars with an automatic transmission.Drop the splash guard and pull the plastic tabs closest to the fender well from under the car. You're going to need a 22mm wrench to remove the sensors, and the wiring harness is hard AF to remove. You may have to pull the large metal brace down, it's just 2 12mm bolts (one front one rear) holding it up. Then you'll have full access to everything.633. 176K views 8 years ago. 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...They also list a Y pipie and other exhaust pieces most from Stainless Steel and reasonable (cheap by Subaru standards ) eBay Motors: Subaru Legacy / Outback / Impreza catalytic converter (item 190275009482 end time Feb-16-09 12:01:44 PST)Right now I only have a confirmed P0420 code. My CEL is actually on now. In the past only a pending code would illuminate the CEL. ... We’re the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. Show Less . Full Forum Listing.Right after I got the new PAK file, my car threw a P0420 code. ... We’re the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. Show Less . Full Forum Listing.That has fixed the P0420 code for me multiple times on several different Subies. It's a small investment compared to replacing the entire cat. ... We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester.CLEAN Your CAT - Fix stubborn P0420 Here's what I did: On 2005 Forester XT with P0420, 1. Removed downpipe/catalytic converters. 2. Separated into upper Cat and lower Cat. 3. In a 5-gallon bucket, mixed 4 gallons water, 10 oz. Citric acid and 7 oz Oxalic acid. (Purchased on Amazon - $20) 4. Soaked main Cat in acid overnght, rinsed completely ...Dec 26, 2009 · 2.5x_sleeper. 45860 posts · Joined 2007. #5 · Dec 26, 2009. My guess is a failing front O2 sensor, causing an over rich condition. This would give you the gas smell & would overwhelm the CAT. The rear O2 sensor, which monitors the CAT, would give you the P0420 CEL code. Sounds like what happen in my '03. :wink:I have 2007 forester with 49000 miles I am reading code P0420 anyone has had any issues with this. ... Newer Generations of Subaru discussion ; 1990 to Present Legacy, Impreza, Outback, Forester, Baja, WRX&WrxSTI, SVX ; P0420 P0420.This low kilometer Subaru Impreza flags a P0420 Catalyst efficiency fault code very quickly. The rear O2 sensor would behave almost like the catalytic conver...Надоела ошибка p0420… — subaru forester (sf), 2,5 л., 1999 годаExplained engine ('09-'13)Subaru p0420. Check Details D fit c c br po420 f ia l ok c $145.45 anais.tn. Subaru check engine light and code # p0420 explained('06-'08) Had a test done at auto zone engine light on results on computer testerSubaru p0420.The P2097 code indicates that the post-catalyst fuel trim system is too rich in bank 1. The Heated Oxygen Sensors (HO2S) are used to monitor the oxygen content of the exhaust stream. The Engine Control Module (ECM) uses the HO2S voltage to determine the air to fuel ratio. An HO2S voltage that increases above bias voltage toward 1 000 mV ...Taking a walk in a forest can be deeply calming. Even if it’s just off the beaten path and you’re swatting mosquitoes away, you’re someplace different than the houses and buildings...If you want to make a combined solution of both of them, just mix the above solutions together. Here is the same thing it English units: 0.1M citric acid solution = 2.56 ounces citric acid in one gallon of total solution. 0.1M oxalic acid solution = 1.20 ounces oxalic acid in one gallon of total solution.May 19, 2021 · Diagnostic trouble code(DTC) P0420 stands for “P0420 Catalyst System Efficiency Below Threshold (Bank 1).”. It indicates that the exhaust system’s oxygen levels are below the required threshold in Bank 1, which can damage the engine’s exhaust and fuel system. Bank 1 refers to the side of the engine that houses the number one cylinder.My P0420 showed up shortly after and never went away. Fix the HG first or you'll just wreck the cat again. Here are the steps I took: Purchased:-Hardware gasket for and of the ... We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. .... P0420 Subaru Catalyst System Efficiency Below ThresholVehicle : 2009 Subaru Forester Touring - Non turbo - Canadian versi 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.I figure I'd give this thread a quick update. We did the catalytic converter stew with citric and oxalic acid in July of 2019, and our 2002 Forester, which previously had a nagging problem, has been P0420-free ever since. 18 months and counting... ~ Silke ~. '02 Forester S 5MT - "Cooper". '11 Honda CR-Z 6MT - "Kat". As for the P0420, here's my theory (which fits your The P0420 is the only code and it just started. The last on the VIN are 4H748003. ... We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of the Subaru Forester. Show Less . Full Forum Listing. Explore Our Forums.2006 Subaru Forester X, 2.5 non turbo, automatic, 288K miles. In the past, I started experiencing P0420 codes around 190K miles. After experimenting with different gas tank potions and solutions (even the popular $5 fix) and after replacing the A/F and downstream O2 sensor, I elected to replace the entire exhaust system. Subaru's warranty covers up until 8 years ...
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