Jay Safford. Automotive Mechanic. 16 years of experience. The code P0420 can be caused by the catalyst, O2 sensors before and after the catalyst. If both O2 sensors and catalyst was replaced then you may have an exhaust leak at the manifold or pipes. I suggest you have a mechanic like one from YourMechanic do a complete diagnostics of …I've got a 2016 Hyundai Accent hatchback 1.6L, and I've had the worst time with this P0420 code that has came on. It says Catalytic efficiency bank 1, and I'm not sure what to do to fix it. I've heard the Cat lasts like forever, so I'm hesitant to just replace it without finding the underlying issue.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. When they see that the converter is not "cleaning" the exhaust enough to meet specs, the Converter is deemed "below threshold" and the P0420 is set.Detailed information on the P0420 dtc trouble code. Includes why it happens and how to fix your car. Trouble Code - P0420 Catalyst System Efficiency Below Threshold (Bank 1) ... I have 2002 Hyundai Santa Fe 2.7 AWD, 142, 000 with code PO420, that also gets poor mileage since code began coming on, and frequently goes off by itself(but not …How to fix you emissions p0420 code for cheap, easy, fast. Watch this video and learn how to turn off you cars check engine in under 10 minutes with parts av...This page is meant to help you troubleshoot the Hyundai Tucson P0430 trouble code. It covers the P0430 code's meaning, symptoms, causes, and possible solutions. P0430 is an emissions-related trouble code and is virtually never a breakdown risk. ... If the code changes to P0420, that would indicate that one of the O2 sensors is …A Hyundai Accent Catalytic Converter Replacement costs between $869 and $900 on average. Get a free detailed estimate for a repair in your area. Find Repair LocationFailed catalytic converter: A failed catalytic converter is the most common cause of a P0420 code. While some catalytic converters fail from age or high milage, the majority of failures are a byproduct from an underlying issue. The most common issue being an excessive rich condition caused by a misfire or fuel trim problem.HyundaiP0420 Hyundai DTC P0420 Make: Hyundai Code: P0420 Definition: Catalyst System Efficiency below Threshold (Bank 1) Description: Engine started, vehicle driven at a speed of 45-60 mph for 8-10 minutes in closed loop, and the ECM/PCM detected the rear HO2S-12 switch rate was similar to the front HO2S-11 switch rate for over 3 seconds …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 engine …Have a 2001 Hyundai Elantra; have a P0420 code. Replaced down-line O2 sensor, then the MAP sensor and code still persists. Had a minor leak in flex pipe, which was fixed (codes not reset, and run for … read moreBad gas cap or the purge valve which is part of the vacuum system is going bad and intermittently tripping the code. I just replaced this on my moms 2008 Jeep patriot last weekend for the same code. Problem solved for about $35. Use your OBD2 reader to clear the code and then drive it on the highway for about 30mi. So it has time to cycle the ...7 posts · Joined 2016. #1 · Jan 26, 2016. Check engine light on my (gfs) 2007 Accent has been on since she bought it from private party. The code is P0420 - Catalytic...Bank 1 *see photo*. Today I changed the plugs, which were not in great shape.=====Claim your FREE engine code eraser 👉 https://free.nonda.co 👈== How to Fix P0420 =====Engine Code P0420 Saving Repair Part...P0420: Inefficient Catalytic Converter(s), Defective Front or Rear Oxygen Sensor(s), Misfiring engines: P0430: ... For more information on Hyundai OBD-II trouble codes, contact us today at 855-757-3265 to speak with one of our knowledgeable service teammates, or schedule a service appointment with our online form. ...About the Problem. After a engine review my conectors of Oxygen Sensor 1 (Pre Catalystic) has broken (crumbles itself). Now i got some problems like Check Engine LightOn, Strong Gasoline Smell and code P0420 (Catalytic converter system, bank 1 - efficiency below threshold). After that, i reconnected the wires following the colors before …P0420. Afternoon, I've got the dreaded P0420 code. Gas mileage has gone down, now only 12-14 around town and used to be 15-17 before. It's a 2008 DGC SE with the 3.3 Flex Fuel and about 251,000 miles. I'm the original owner and the Cat has never been changed since new.2007 Hyundai Santa Fe. Check engine light is caused by P0420. Troubleshooting tips.Scan tool: US: https://amzn.to/3QYEACrCanada: https://amzn.to/3WvrEVM .Th...The P0420 code indicates that your vehicle’s powertrain control module (PCM) monitors the poor efficiency of the catalytic converter at Bank 1. This code may also be triggered due to a bad catalyst or a false alarm caused by a faulty oxygen sensor at Bank 1. Basically, Bank 1 and Bank 2 are the two sides of the engine.Next time I will need to take my car to a Hyundai Dealer if it comes up. ... I have the p0420 code I had all 02 sensors changed and 1 converter changed!!! Should I ...Mar 16, 2016 ... Go to channel · How To Diagnose A P0420 Catalytic Converter Low Efficiency Code Plus Exhaust Leak Testing. GoTech•939K views · 13:55. Go to ...The P0420 code in Hyundai Veloster refers to a malfunction in the catalytic converter efficiency. This code indicates that the catalytic converter is not working as …10163 posts · Joined 2009. #2 · Sep 25, 2021. It's the post cat sensor that trips the P0420. If you can monitor the post cat O2 sensor voltage when warmed up and at a steady speed. It should be held steady above .550v or so, usually near .700v. the volts will drop when you let up on the throttle for any length of time.Aug 20, 2020 · Code P0420 Hyundai Description. The catalyst’s efficiency is demonstrated by its ability to oxidize CO and hydrocarbon emissions. The Powertrain Control Module ( PCM) compares the output signals of the front and rear oxygen sensors to determine whether the output of the rear sensor is beginning to match the output of the front oxygen sensor. The most common fix for P0420 in the Hyundai i10 is a new catalytic converter, followed by an O2 sensor replacement. Before taking your i10 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 Hyundai i10: 1. Check for Other Codes.That usually means a failing converter, but it's a part covered by federal emissions for 8 years/80k miles. If you live in California it could be longer. If you are still under 80k miles I would take it to the dealer since the parts would be covered. This is an older thread, you may not receive a response, and could be reviving an old thread.CODE P0420 CHECK ENGINE LIGHT ON FIX HYUNDAI KIA, CATALYTIC CONVERTER FIXIf you have Hyundai Sonata and you have check engine light and code P0420 Catalyst E...A logged P0463 code means that a high voltage signal is detected from the fuel level sensor, resulting in inaccurate fuel gauge readings. A faulty fuel level sensor circuit or sending unit, damaged body computer, PCM issues, and a faulty smart fuse box are common reasons why this code is triggered. Aside from inaccurate fuel level …A logged P0463 code means that a high voltage signal is detected from the fuel level sensor, resulting in inaccurate fuel gauge readings. A faulty fuel level sensor circuit or sending unit, damaged body computer, PCM issues, and a faulty smart fuse box are common reasons why this code is triggered. Aside from inaccurate fuel level …The P0420 code is related to the catalytic converter. When this code appears, it indicates that there is a problem with the efficiency of the catalytic converter. ... See also Efficient Emissions Control: Hyundai Veloster N's System Inspection. Can a faulty oxygen (O2) sensor cause the P0420 code in my Kia? Yes, a faulty oxygen (O2) ...The most common fix for P0420 in the Hyundai Tiburon is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Tiburon 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 Hyundai Tiburon: 1. Check for Other Codes.This page is meant to help you troubleshoot the Hyundai Veloster P0420 trouble code. It covers the P0420 code’s meaning, symptoms, causes, and possible solutions. P0420 is the most common OBDII code and is virtually never a breakdown risk. A failing oxygen sensor or bad catalytic converter are the most common causes of P0420. …The code was P0420. I took it to Meineke, and they replaced the catalytic converter, as well as two oxygen sensors and two O2 sensors (this is according to the invoice also). It was fine for the last almost seven months, and then two days ago, the check engine light came back on with the same P0420 code. Parts and labor are warrantied for a ...2008 hyundai accent runs rough P0420 code. co0de p 0420 refers to vat converter bank 1 below threshold ===causes ---cat converter---wiring ---HO2S ( heated oxygen sensor in the exhaust manifold bank 1 before the cat converter) you have possible 2 problems. 1--- the HO2S is faulty but that alone will not result in what you describe.When the P0420 code appears, the catalyst system efficiency is below the threshold for a particular engine bank, often referred to as Bank 1. This code is related to the vehicle's catalytic converter and oxygen sensors. The primary purpose of a catalytic converter is to reduce harmful emissions from the engine by converting toxic gasses, …Yes, partially; the Hyundai Motor Company owns about a third of Kia Motors. Both Kia and Hyundai are large automobile makers originally based in South Korea. Hyundai is the largest...The codes being thrown are P0420 P2195 and P1166 on a 2004 hyundai elantra. Is this simply the primary o2 causing all of this havoc or a combinat … read moreHyundai dealers, corporate reps, etc, please message the mods about an official flair. ... 2013 coupe check engine light p0420 code help upvotes ...P0420: Inefficient Catalytic Converter(s), Defective Front or Rear Oxygen Sensor(s), Misfiring engines: P0430: ... For more information on Hyundai OBD-II trouble codes, contact us today at 855-757-3265 to speak with one of our knowledgeable service teammates, or schedule a service appointment with our online form. ...Hyundai dealers, corporate reps, etc, please message the mods about an official flair. ... 2013 coupe check engine light p0420 code help upvotes ...in this video I will share with you how to diagnose and fix the cause of a P0420 and P0430 Trouble Code on a Hyundai Sonata#Catalyticconverters #Catalyticcon...March 2, 2020 by Jason. P2096 is a generic OBD II code, which means that it has the same meaning for the Hyundai Elantra as it would any other vehicle. It specifically indicates that your Elantra detected that it is running too lean (too much air for the amount of fuel present). Bank 1 is the side of the engine with the first spark plug in the ...Hyundai Sonata P0420 OBDII Code Defined. P0420 is generic (has the same meaning for all vehicles made in 1996+) OBDII trouble code. Here’s the technical definition for your car: P0420: Catalyst System Efficiency Below Threshold (Bank 1) Catalyst System Efficiency. Your Sonata’s exhaust contains hydrocarbons, carbon monoxide, and other ...98 explorer codes p0420, p0174 Hello. 98 explorer with code P0420(catalyst system efficiency below threshold)(Bank1) and P0174 (System too lean)(Bank2) The explorer idles very rough in cold weather, dont want to stay running until it warms up. Also you hear it almost like misfiring every 30 seconds, it its more of a tick, an...10163 posts · Joined 2009. #2 · Sep 25, 2021. It's the post cat sensor that trips the P0420. If you can monitor the post cat O2 sensor voltage when warmed up and at a steady speed. It should be held steady above .550v or so, usually near .700v. the volts will drop when you let up on the throttle for any length of time.Here’s a good P0420 diagnostic order for the Hyundai Genesis: 1. Check for Other Codes. The first thing you want to do when trying to fix P0420 in the Genesis is to verify there aren’t any other trouble codes. Three types of codes can give clues as to what’s going on with your car. Misfire Codes.P0420 code. Catalyst Effeciency Below Norma (Bank 1) This was the explanation I got from autozone. First question is how serious is this? ... Hyundai Forum is a community for all Hyundai Owners to talk and learn all about their favorite subject: Hyundai cars from the Sonata to the Elantra and even the new Kona!P0420 HYUNDAI Code: Meaning, Causes, and Symptoms | OBD2 Codes. P0420 HYUNDAI – Warm Up Catalyst Efficiency Below Threshold Bank 1 . P0420: DIY Repairing Video TutorialDoes Cataclean really fix a P0420 / P0430 error code and catalytic converter. Cataclean Link: https://amzn.to/33t8RVQ Second channel for easy to follow Home ...When you set up an HP printer as a network printer, you should consider if you want to set up security for the printer. To do so, you need to set or at least identify, the administ...If the frequency ratio of front and rear HO2S is higher than threshold value, the PCM determines that a fault exists and the P0430 code is stored. Possible symptoms. - Engine Light ON (or Service Engine Soon Warning Light) P0430 Hyundai Description. The catalyst’s efficiency is demonstrated by its ability to oxidize CO and hydrocarbon ...P0420 code. Jump to Latest Follow. 601 views 4 replies 4 participants last post by Majestictobil Apr 3, 2024. Majestictobil Discussion starter. 4 posts · Joined 2021. #1 · Feb 11, 2024. I have a 2013 Hyundai accent and I replaced the cat 2 weeks ago because it was throwing a p0420 code and went into a limp mode and it’s throwing the same ...8252 posts · Joined 2009. #4 · Dec 16, 2012. Once again P0420 caused by. - Catalytic converter deterioration or malfunction. - Exhaust system leaks. - Loose front or rear HO2Ss. - Faulty front heater O2 sensor. - O2 sensors harness is open or shorted. - O2 sensors poor electrical connection Help with this.2016 Elantra 1.8, P0420 only w/ new cat and O2's. I purchased a 2016 Elantra Limited 1.8 w/86k yesterday from a BHPH lot, so no warranty. I did a thorough inspection of the car and everything seemed good. I was allowed to test drive the car with no employee or salesperson. From start up to shutdown, test drive included, the engine was running ...Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases the catalytic convert needs to be replaced to fix the problem. If the P0420 code is combined with other codes, try fixing the other codes first. ⚠ Check if your Hyundai have …Here’s a good P0420 diagnostic order for the Hyundai Genesis: 1. Check for Other Codes. The first thing you want to do when trying to fix P0420 in the Genesis is to verify there aren’t any other trouble codes. Three types of codes can give clues as to what’s going on with your car. Misfire Codes.The P0420 code on a Hyundai refers to a diagnostic trouble code that indicates a problem with the efficiency of the catalytic converter. The code specifically …The p0420 code is an important warning signal in your hyundai accent that relates to the check engine light. The code indicates a problem with the catalytic …May 8, 2018. #7. You can't "clean" a cat unless it's clogged with oil. More often than not, the honey comb inside melts. You can't unmelt the metal. You can either hollow it out and use an o2 anti-fouler and pray that the code goes away, or fix it the right way by replacing the cat. S.A somewhat common issue with the Hyundai Tucson is the P0449 code. This code references a number that is given to you when you plug it into a OBD2 scanner. P0449 deals with the evaporative emissions control (EVAP) system. It often appears with, or is related other codes, such as P0420, P0446, and very often P0455.Although they both use an “H” as their company logo, Honda and Hyundai are different companies based out of different countries. Honda is based out of Japan, whereas Hyundai is bas...I have a 2019 Hyundai Tucson with a 2.0L GDI (no turbo) About 6 months ago, after a road trip of about 700 miles, the P0420 code came up, car was at 55k miles. I thought it was a fluke and cleared the code. 6 months and 3000 miles later, the code came back. This time, I did more digging and looked at the data from the vehicle.I believe your car should still have a manufacturer warranty though, you’re within that 5 yr/60,000 miles or so that the car is covered for. You’ll probably be able to get it fixed at the dealer for free. P0420 codes are related to emissions systems problems, specifically that code is for catalytic converter failure.I've been getting periodic P0420 Check Engine codes on Bank 1. Upon some research, many are of the opinion that this 1 (of the 3) catalytic converters going bad. ... Hyundai Forum is a community for all Hyundai Owners to talk and learn all about their favorite subject: Hyundai cars from the Sonata to the Elantra and even the new Kona!98 explorer codes p0420, p0174 Hello. 98 explorer with code P0420(catalyst system efficiency below threshold)(Bank1) and P0174 (System too lean)(Bank2) The explorer idles very rough in cold weather, dont want to stay running until it warms up. Also you hear it almost like misfiring every 30 seconds, it its more of a tick, an...A $200 million Hyundai and Kia settlement compensates vehicle owners whose cars were stolen as a result of lackluster anti-theft features. By clicking "TRY IT", I agree to receive ...1998 hyundai accent: engine light came..10 min..same code for the cat I have a 1998 hyundai accent the engine light came on I had it checked it showed a bad front cat. the service department at hyundai told me to unhook the batt. cable and put them together for 10 min t …20-FL-010H. Title: TUCSON 2.0L DTC P0420 - ECM UPDATE AND CATALYST REPLACEMENT. Date: 10/20/2020. Models: 2019Tucson. Summary: This bulletin provides information related to the repair of DTC P0420 "Catalytic Converter System Bank 1 - Efficiency Below Threshold" found stored in the Engine Control Module (ECM).It’s an aftermarket cat I bought for $200. Even got a new oxygen sensor for upstream that was $160 new. That may be the issue. I know the Hyundai cat is pretty expensive. I replaced the catalytic converter last year in September and it fixed my P0420 code up until now today I have a check engine light for the same code….6/25/2020: I got the P0420 code again. Oh, well--at least I had 7 good months! To add: ... Hyundai Forum is a community for all Hyundai Owners to talk and learn all about their favorite subject: Hyundai cars from the Sonata to the Elantra and even the new Kona! Show Less .JOIN GASDIESEL GARAGE AS WE DIAGNOSE AND REPAIR THE MOST COMMON CHECK ENGINE LIGHT TROUBLE CODE P0420 Catalyst Efficiency Below …This page is meant to help you troubleshoot the Hyundai Accent P0420 trouble code. It covers the P0420 code’s meaning, symptoms, causes, and possible solutions. P0420 is the most common OBDII code and is virtually never a breakdown risk. A failing oxygen sensor or bad catalytic converter are the most common causes of P0420. Table of Contents8252 posts · Joined 2009. #4 · Dec 16, 2012. Once again P0420 caused by. - Catalytic converter deterioration or malfunction. - Exhaust system leaks. - Loose front or rear HO2Ss. - Faulty front heater O2 sensor. - O2 sensors harness is open or shorted. - O2 sensors poor electrical connection Help with this.Sometimes, when you see O2 sensor related codes, fixing those might also fix the code P0420. If the code P0420 is the only code present, visually inspect any exhaust leaks before the rear O2 sensor. An exhaust leak may mislead the O2 sensor and trigger the code. If you find any broken, cracked or disconnected hoses, replace them and fix the code.=====Claim your FREE engine code eraser 👉 https://free.nonda.co 👈== How to Fix P0420 =====Engine Code P0420 Saving Repair Part...What to do when you get a P0420 catalytic converter code. If you’ve got a check engine light with either a P0420 P0420 catalytic converter code or a P0430 trouble code, don’t automatically replace the oxygen sensor. Why? Because a herP0420 catalytic converter code is almost NEVER caused by a bad oxygen sensor. Here’s a step by step …What are the Possible Causes of the P0420 Code? Inefficient catalytic converter; Defective oxygen sensor; Damaged wiring; Loose connections; Exhaust leak; …The code was P0420. I took it to Meineke, and they replaced the catalytic converter, as well as two oxygen sensors and two O2 sensors (this is according to the invoice also). It was fine for the last almost seven months, and then two days ago, the check engine light came back on with the same P0420 code. Parts and labor are warrantied for a ...P0420 code and O2 Sensor replacement. So my 2003 Elantra has been getting horrible gas mileage, running super rich. I had a constant P0420 catalytic emissions code and one misfire reading. I'd clear it and it'd go away for about an hour and come back. I feared I would have to replace my whole exhaust manifold/cat part until I read this …Hyundai OBD II P0420 Trouble Code. The Hyundai Elantra, Santa Fe, Sonata, and Tucson can all exhibit P0420 codes. Hyundais tend to have less efficient converters than other makes, leading to more failures. Expect to replace the converter at some point to clear P0420 permanently.This page is meant to help you troubleshoot the Hyundai Veloster P0420 trouble code. It covers the P0420 code’s meaning, symptoms, causes, and possible solutions. P0420 is the most common OBDII code and is virtually never a breakdown risk. A failing oxygen sensor or bad catalytic converter are the most common causes of P0420. Table of Contents13 posts · Joined 2020. #1 · Sep 26, 2022. Hello everyone, I have 2012 Hyundai Accent and been receiving the P0420 code few times. It stays on for 2-3 days and then goes out automatically. I have noticed the code comes back after driving on a very hot day or after driving aggressively.This page is meant to help you troubleshoot the Hyundai Accent P0420 trouble code. It covers the P0420 code’s meaning, symptoms, causes, and possible solutions. P0420 is the most common OBDII code and is virtually never a breakdown risk. A failing oxygen sensor or bad catalytic converter are the most common causes of P0420. Table of ContentsIndian Twitter users to trend #BoycottHyundai. Update: The South Korean government has reacted to the controversy saying it “regretted the offence caused to the people of India” ov...Causes of a Hyundai P0133 Code: O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)Hyundai Altos P0420 OBDII Code Defined. P0420 is generic (has the same meaning for all vehicles made in 1996+) OBDII trouble code. Here’s the technical definition for your car: P0420: Catalyst System Efficiency Below Threshold (Bank 1) Catalyst System Efficiency. Your Altos’s exhaust contains hydrocarbons, carbon monoxide, and …For example, the diagnosis for a code P0326 on a Hyundai may differ from the same logged code on a Toyota. Err on the side of caution by referring only to repair and diagnostic information specific to your vehicle. ... OBD2 Codes 101; P0420 Code; P0430 Code; P0300 Code; P0455 Code; P0401 Code; P0172 Code; P0446 Code; P0011 Code; P0340 Code ...
The P0420 code on a Hyundai Tucson typically indicates a problem with the catalytic converter. This code is a generic powertrain code that may appear in various makes and models. The P0420 code specifically refers to a catalytic converter efficiency below the threshold.. Publix northridge
Or the sensor from your car into an Accent without any P0420 code. A conclusive test of the catalytic converter is to measure the temperature with an infrared thermometer at the inlet of the cat and at the outlet. Since the converter is burning leftover products of gas the temperature should be higher at the outlet than the inlet.The P0420 code in Hyundai Veloster refers to a malfunction in the catalytic converter efficiency. This code indicates that the catalytic converter is not working as …10 posts · Joined 2007. #1 · Nov 8, 2013. Hi guys. I recently got a diagnostic computer check on my 2005 Hyundai Elantra 4DSD that has over 95,000 miles and got the code P0420 showing the following: 1. Catalytic converter defective due to. 2. Engine misfire or running condition. 3.This hyundai has replaced a 2000 Honda Civic EX. Now I got the code reader and read the code. P0420. I had this code with the Honda before and the fix was an OEM catalytic converter. That was around $750.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...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.This page is meant to help you troubleshoot the Hyundai Santa Fe P0430 trouble code. It covers the P0430 code's meaning, symptoms, causes, and possible solutions. P0430 is an emissions-related trouble code and is virtually never a breakdown risk. ... If the code changes to P0420, that would indicate that one of the O2 sensors is …The codes being thrown are P0420 P2195 and P1166 on a 2004 hyundai elantra. Is this simply the primary o2 causing all of this havoc or a combinat … read morePesky P0420 Keeps Returning. I have a 2005 Hyundai Elantra GLS that keeps throwing a P0420 code. No other codes just the P0420. Vehicle has 147,000 miles and runs great. Getting 30 MPG even with the P0420. Plugs and wires only have 28,000 miles on them. No exhaust leaks anywhere.The P0420 code is a common diagnostic trouble code that indicates a problem with the catalytic converter in the Hyundai Santa Fe. When this code appears, it …Code P0420 Hyundai Description. Code P0420 for a Hyundai describes how the efficiency of the catalytic converter is determined by its ability to oxidize CO and hydrocarbon emissions. The …I believe your car should still have a manufacturer warranty though, you’re within that 5 yr/60,000 miles or so that the car is covered for. You’ll probably be able to get it fixed at the dealer for free. P0420 codes are related to emissions systems problems, specifically that code is for catalytic converter failure.This page is meant to help you troubleshoot the Hyundai Tucson P0420 trouble code. It covers the P0420 code's meaning, symptoms, causes, and possible solutions. P0420 is the most common OBDII code and is virtually never a breakdown risk. A failing oxygen sensor or bad catalytic converter are the...The most common symptom reported for the P0420 error code is an illuminated check engine light. You may also hear a loud exhaust noise with the P0420 …P0420 code. Jump to Latest Follow. 601 views 4 replies 4 participants last post by Majestictobil Apr 3, 2024. Majestictobil Discussion starter. 4 posts · Joined 2021. #1 · Feb 11, 2024. I have a 2013 Hyundai accent and I replaced the cat 2 weeks ago because it was throwing a p0420 code and went into a limp mode and it’s throwing the same ....