P0420 subaru forester

Subaru of America, Inc. (SOA) has determined that vehicles affected by this Service Program require ECM reprogramming. ... performed with over 100,000 miles and the Check Engine light illuminated with DTC P0420 in the ECM memory. The catalytic converter efficiency test must also indicate replacement is necessary. For all other vehicles, the ...

And it was the same as usual, P0420 and P0442. I've had P0420 since I got the car in june 2011, but didn't bother as, according to my mechanic, "it's just because the computer doesn't recognize the aftermarket catalyst". Back then, gaz mileage was on close to manufacturer's specs (11L per 100km city = 21MPG, ~9L/100km highway = 26MPG) so I ...1995 Subaru Legacy L 2.2L with p0420. Problem: Check engine light (P0420), Hesitation, Cuts out, Stall ... 2002 Subaru Forester S 2.5L: Replace CAT: 1997 Chevrolet Blazer 4.3L: Replace CAT: 2005 Nissan Altima S 2.5L: Replace CAT: 1997 Mercury Grand Marquis LS 4.6L: Replace CAT: 1996 Ford E250 4.9L: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 ...OutbackJon said: P0420 is triggered by the downstream sensor. I've fixed it four times on three different Subarus by replacing that sensor. (The Subaru that I had to do it twice on, it was about 120k miles between fixes, and the second time it was the sensor on the other side of a 3.6R exhaust.) I have been trying to justify purchasing this ...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 Sienna ...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.That is the issue with the P0420. Resident Adviser @ WTF Tuning, LLC 2002 FORESTER S 1998 FORESTER S. Save Share. Like. scarmack. ... Subaru WRX Forum. 3.2M posts 153.2K members Since 2001 We invite you to join our Subaru Impreza WRX and STi community to discuss engine mods, builds, detailing, and more. ...

My 06 Forester spit out the p0420 code the other day while i was driving down the highway. Ive been doing alot of reading on here and I know it could be one of the 2 oxygen sensors or the 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 ...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.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).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.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.Here's my situation. I am throwing a p0420, after long drives, but now after about 7 months, it throws often. ... 1999-2005 Subaru Forester Catalytic Converter - EvanFischer REPS960301 - Single, Powdercoated silver, 49-state legal - no CA shipments, OE replacement

For the past six months or so on my 02 Forester L, my CEL has been going off and on. When on, it gives the P0325 and P0420 codes. I know what these represent; what I don't know is whether there might be a relationship between the two. That is, what might cause them to go on and off at the same...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.The C0057 Subaru code corresponds to a problem with the steering angle sensor calibration. When this code appears, it means that there is a discrepancy between the calculated steering angle and the actual steering angle of the vehicle. This issue can lead to various problems, such as incorrect stability control intervention and compromised ...Aug 24, 2007 · 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.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.comP0172 is running too rich. C1422/C1424 seemed related to O2 sensor. Minor things you can do to help overfueling (there's tutorials out there for all of this, google is your friend): Clean AFM. Clean EGR. Clean throttlebody. Clean PCV. Replace oil (sometimes oil gets contaminated with fuel apparently from lots of short drives, and causes issues ...

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#1 · 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 …The Subaru Forester is a popular choice among families and outdoor enthusiasts alike. Known for its reliability, versatility, and off-road capabilities, the Forester also excels in...Jun 12, 2019 · 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...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 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.In-dash shows P0700, P1710 and C0140. I used the Bafx and torque pro to clear the codes, it didnt clear the P0700 nor the P1710. This is a first for these codes after the new ECM. Prior to the new ECM codes were P0420 (Cat system efficiency below threshold) P0306 (Misfire cyl 6) and P2503 (Alt Circuit Low).

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.Jun 12, 2019 · 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...Service Bulletin18-023. June 21, 2018Version 1. Warranty Extension: DTC P0420 or P0430 (CA, CT, ME, MA, NY, and VT Only) AFFECTED VEHICLES Year Model Trim VIN …It also has a CEL, P0420, cleared once and returned, so I started by replacing the down stream 02 sensor, (Denso) but the light was still on after his 200-mile trip back to Lynchburg. ... 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.This turned out to be a bad ignition coil. Replaced it, and the car runs and drives great. After about 50-100 miles of driving, it threw the P0420 code. (with a bunch of other dash lights like I read the subarus do). seems to run fine. I have an OBD2 adapter and Torque pro, and I did a few readings. One screenshot is idle, one is around 2k RPMS.I pulled a P0420 code (Catalyst System; Bank 1: Efficiency Below Threshold) from our 2005 Impreza Outback Sport (EJ253 with 5 speed manual) yesterday. ... 1990 to Present Legacy, Impreza, Outback, Forester, Baja, WRX&WrxSTI, SVX; All Activity; Home ; Newer Generations of Subaru discussion ; 1990 to Present Legacy, Impreza, Outback, Forester ...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 ...P0420 is the code for "Catalyst system efficiency below threshold ". The ECU determines that by monitoring the voltage output of the second (rear) O2 sensor. The output of the front sensor is supposed to oscillate (once the engine is warm enough for the system to be running closed-loop).

p0420 road test I got the subaru procedure for the p0420 test. I'll check the scanner graphs after I road test and post results. Save Share. Like. 161 - 180 of 887 Posts ... 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.

The corrosion in this cable was causing a loss of 250 amps between the battery and block. Enough to cause problems with all the drivetrain controls, effecting performance and leading up to a P0420 code. Block end by starter. Battery end (He had cut off the original clamp and added a new one, but, when I tested the cable I was losing 250 amps ...Please 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...This Service Information Bulletin announces diagnostic service procedures to be followed when DTC P0420 (Catalyst System Eficiency Below Threshold Bank 1) is detected by …Друзья расказываю один из способов победить ошибку р0420.When the pressure inside of the fuel tank is too high, P0453, is thrown and the check engine light comes on. If the only trouble code that you have is P0453, your Forester is in no risk of breaking down. The EVAP system is responsible for migrating fuel vapor. Whether it is doing that or not, has no effect on the way your engine runs.P0420 code is the rear sensor reading the O2 levels coming out of the cat are higher than what should be. (possible failing Cat) good sensor. P0136 is the computer reading a problem with the sensor. Just did a PO136 on a ladies 2001 Forester. Changed rear sensor for $124 for part from Subaru and 20 minutes labor.Ran the code and got " P0420 - Catalyst System Efficiency Below Threshold Bank 1". ... We’re the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability history of …It will mask issues that should be addressed. Normally, the $5 fix is used when the only issue is the P0420 CEL code. Bobby... ['07 FSXT Member Journal] ['03 X Member Journal] 2007 Forester Sports XT - COBB ... We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications and reliability ...

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Running overly rich can cause a P0420 CEL code. We haven't seen that CEL code since the 5$ fix was installed. :biggrin: The normal installation is to drill out (1/2") one spacer... has to be done so the O2 sensor tip will fit. ... We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester, modifications ...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.I'm very new to these Forester hells having just gotten a 2010 and recently got the dreaded P0420 code. In Youtubes suggesting several possible solutions the catalytic converter cleaner added to 1/4 full fuel tank was the first suggestion. Do any of you have successful experience with that, or terrible experience with that like it ate gaskets ...I'm very new to these Forester hells having just gotten a 2010 and recently got the dreaded P0420 code. In Youtubes suggesting several possible solutions the catalytic converter cleaner added to 1/4 full fuel tank was the first suggestion. Do any of you have successful experience with that, or terrible experience with that like it ate gaskets ...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 .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...After reading most if not all of Cardoc's 1000+ page bible on the P0420 codes, and doing much of the testing (as best I could), I thought I'd ask for a bit of advise. ... 2009 Forester 2008 Outback 2.5i 130K PIA, 2010 Outback 2.5 103K, 139K, 156K, 192K ... I guess first / next step is to get an O2 sensor and a real live Subaru AF sensor. That ...The Subaru Forester is a popular choice among families and outdoor enthusiasts alike. Known for its reliability, versatility, and off-road capabilities, the Forester also excels in... ….

Here is my story. I have an 01 S with manual trans with 227,000 kms. Forester has always been maintained at the dealer. This past winter I started getting an intermittent P0420 code. If i used premium gas it triggered every 3 weeks or so. If i used regular gas it tripped pretty much once a week ( i fill up approx every 5 days).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 P0420 code can actually point to a lot of different things. In a rush to head out of town, I got an oil change at a subpar quick lube place, and got a P0420 code about 100 miles down the road. Took it over to a buddy's place when we got back into town, and he said "this cheap oil filter is probably throwing the code".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 …In all seriousness, the P0420 is only good for making your wallet lighter by either ~$100 for a new sensor or several times that for a new 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.2017-18MY Forester 2.5L 2019-23MY Forester 2018-23MY WRX 2019-21MY Ascent SUBJECT:DTC P0420 Diagnostic Procedure INTRODUCTION: This Service Information Bulletin announces diagnostic service procedures to be followed when DTC P0420 (Catalyst System Efficiency Below Threshold Bank 1) is detected by the Engine Control Module (ECM).Petrochemical giant Ineos was granted a permit to cut down a wood to build a new plastic plant in Antwerp. A provincial government in Belgium on Thursday (November 7) granted Europ...Pulled p0420, replaced rear o2 sensor. Still had p0420 so did $5 fix. Pulled codes p0420 p0031. Cleared codes and p0031 kept popping so I replaced front 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 Forester. Show Less .Several factors can trigger the P0420 code in a Subaru Forester. Understanding these causes can help in diagnosing and resolving the issue effectively. … P0420 subaru forester, Forester 2001 L - Stock 101k Miles P0420 - Catalytic Converter Efficiency Below Threshold The forester has been throwing this code for a few months now, typically shows up on long highway runs (but to be fair, that is the vast majority of my driving). I bought a scanner from scantool.net..., 2.5x_sleeper. 45859 posts · Joined 2007. #2 · Apr 13, 2021. @DirtyJack You can't just unplug the sensor, you will get a CEL code. Luckily, on the '04 the rear O2 sensor is only used to monitor the efficiency of the CAT (s). There's a couple ways to fool the system. The $5 fix inserted into the exhaust with the end sealed., GET FIXD. What Does Code P0420 Mean? P0420 definition : Catalyst system efficiency below threshold (Bank 1) Issue Severity: MODERATE – Extended driving with this code can cause internal …, 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., 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 …, 11 posts · Joined 2011. #1 · Aug 22, 2011. My 2002 Forester (5-speed) has been having rough idling issues for a month or so now but now it's undriveable due to lagging, jumping, coughing etc. It sounds like a bad Harley tune. One thing that might help diagnose it is that it only has issue when in gear and under load., Subaru Mechanic: Ronnie. Normally you can replace the front converter without having to replace the downstream converter with no issue. The common one to fail and set the P0420 is, in fact, the front converter. If the only code your getting is the P0420 then I would just replace the front converter and usually, you will be fine with no issue., I have been trying this on quite a few subes with the P0420 catalyst insuffiniency code and it has worked great. It is a simple fix that can be done in minutes. ... 1990 to Present Legacy, Impreza, Outback, Forester, Baja, WRX&WrxSTI, SVX ... Newer Generations of Subaru discussion ; 1990 to Present Legacy, Impreza, Outback, Forester, Baja, WRX ..., 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., After reading most if not all of Cardoc's 1000+ page bible on the P0420 codes, and doing much of the testing (as best I could), I thought I'd ask for a bit of advise. ... 2009 Forester 2008 Outback 2.5i 130K PIA, 2010 Outback 2.5 103K, 139K, 156K, 192K ... I guess first / next step is to get an O2 sensor and a real live Subaru AF sensor. That ..., Get ratings and reviews for the top 7 home warranty companies in Forest, VA. Helping you find the best home warranty companies for the job. Expert Advice On Improving Your Home All..., Stopped by autozone to see what the code was and came up P0420 catalyst efficiency below threshold bank 1. ... I am not sure if this would cover your problem but it may be worth asking a local Subaru dealer. Seagrass . SOA 1-800-782-2783, MY11 Outback 3.6R Premium (Sold Jan 2022), MY12 Forester XT 2.5 (Youngest daughter) MY07 Liberty/Legacy 2.5 ..., 2.5x_sleeper. 45859 posts · Joined 2007. #2 · Apr 13, 2021. @DirtyJack You can't just unplug the sensor, you will get a CEL code. Luckily, on the '04 the rear O2 sensor is only used to monitor the efficiency of the CAT (s). There's a couple ways to fool the system. The $5 fix inserted into the exhaust with the end sealed., 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., 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., The Subaru Forester is a popular choice among families and outdoor enthusiasts alike. Known for its reliability, versatility, and off-road capabilities, the Forester also excels in..., P0420 Code - Catalyst System Efficiency Below Threshold Bank 1. How to Fix. Check the 'Possible Causes' listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins. ... P0420 Subaru Catalyst System Efficiency Below Threshold ..., The P0457 is one of the codes that triggers the CEL only if the fault is detected in two driving cycles. The CEL will go out if the fault isn't detected for three driving cycles, and the code is erased from memory if the fault isn't detected for 40 driving cycles. This can lead to frustration if the fault is intermittent, because by the time ..., 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., 45844 posts · Joined 2007. #4 · Jul 22, 2014. Yes, fixing the P0420 CEL code could improve your gas mileage. The rear O2 sensor on the '03 monitors the exhaust flow for excess 02 & doesn't affect the operation of the engine as it does on the '05+. The P0420 CEL code could be caused by many things, but one is an over rich condition which ..., I'm looking at a 2001 forester s, 5 speed with 147k for a pretty good price ($750). The man selling it told me it needed a cat. When I scanned it the only code that comes up when scanned is the infamous P0420 "Catalyst System Efficiency Below Threshold (Bank 1)"., Infamous06X Discussion starter. 99 posts · Joined 2017. #1 · Jan 28, 2017. so yesterday i get the infamous p0420 code and cruise control was flashing for catalytic converter on the way to the dealership. i get my car serviced and they explain its a $1200 fix for a new cat installed. went home , and SEARCHED here., 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., Forester 2001 L - Stock 101k Miles P0420 - Catalytic Converter Efficiency Below Threshold The forester has been throwing this code for a few months now, typically shows up on long highway runs (but to be fair, that is the vast majority of my driving). I bought a scanner from scantool.net..., 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 ..., Subaru Emissions Performance Warranty (36-month / 60,000-km) Subaru Canada, Inc. guarantees that every Subaru vehicle is designed and manufactured to pass all federal and provincial emissions performance tests and will continue to do so for a period of 36 months from the date of initial registration or 60,000 km, whichever comes first., 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., I recently purchased a 2005 Subaru Forester XS, and it's beautiful! But after driving it 30 miles, the CEL popped on & the Cruise Control Light started blinking. I got home and plugged in my reader to find out it was the lovely P0420. After reading the live data, I saw my "Oxygen Sensor Current (B1-S1)" fluctuates between -127.918 mA & 127.871 mA., P0420 Catalytic Converter Efficiency and C1424 ECM Module Fault are the 2 constants; they have been there every time. As a quick educated guess I am going to say the catalytic converter is failing and sets the ECM fault at the same time. ... We're the best Subaru Forester Owners Forum to talk about the best years of the Subaru Forester ..., 2001 Subaru Outback LLBean P0420 Diag - YouTube ... I was also reminded why I opted out of owning a Forester. You can't just tilt the seat up to get to the harness, and too much to remove from the rear to get to the fuel pump. But it all worked out good. If you're in Austin, TX and having difficulties with the dealer or any shop, hit me up. ..., May 14, 2015 · 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..., Apr 24, 2019 · Subaru Mechanic: Ronnie. Normally you can replace the front converter without having to replace the downstream converter with no issue. The common one to fail and set the P0420 is, in fact, the front converter. If the only code your getting is the P0420 then I would just replace the front converter and usually, you will be fine with no issue., Jun 12, 2019 · 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...