Jeep p0420 code

Code P0420 Jeep: Catalyst System Efficiency Bank 1. Hi guys, need some help for folks that have experienced this. Based on what I have looked up, it looks like a possible bad catalitic converter. I got a check engine light, I put my scanner on it and I erased the code. That cleared the check engine light.

CEL - Code P0420, 1.3k miles, 2015 EcoDiesel built in January. So my 2015 Jeep EcoDiesel threw a CEL on my way back from folks this afternoon, about a 45 minute drive. Hot as Hades here in Central Texas today. Threw the code 5 mins after startup. Ran the OBD-II scanner when I got home, saw it was P0420. Just bought the truck in June, it had ...Save up to 40% on KEH discount code this June 2023. Get new or used camera, lens + tripods for cheap when you use a KEH promo code today for today. PCWorld’s coupon section is crea...Trouble code p0420. Jump to Latest Follow. 6K views 8 replies 3 participants last post by TJerry Dec 9, 2014. gel04tj Discussion starter. 30 posts · Joined 2013. #1 · Dec 8, 2014. Check engine light on with this code, replaced both o2 sensors on manifold (code said bank 1) & I used oem mopar sensors. Had code erased & drove it, check engine ...96XJ 4.0L Check Engine Code PO420. Check engine light came on, had it scanned at the dealership and the local auto hobby shop and came up with the same code, (PO420). The catylitic converter on there was a "Random Technology, Level-1" I had purchased from Quadratec and had installed some years back along with new (2) OEM …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.Jeep Wrangler P0420 Code Possible Solutions Often, the oxygen sensor is the cause of P0420. Specifically it'll usually be the O2 sensor(s) on the upstream side of the catalytic converter. But, don't be surprised if it's not. It would be a good idea to check the exhaust for leaks first.

would try switching to 93 octane fuel, check/replace converter/inverter gasket with the springs. replace 02 sensors with OEM sensors. i just passed inspection this morning. and have had p0420 for 1-2 yrs. This is an older thread, you may not receive a response, and could be reviving an old thread.In this video I replace the rear O2 sensor (bank 1) on a 2008 Jeep Grand Cherokee 3.7 V6. This vehicle has a trouble code P0420 stating the catalyst system e...P0420 Code. Hi, new to the forum and new Jeep owner. I've got a 2007 Grand Cherokee Limited with the 5.7. I had it checked out before I bought it and it showed a fault with a downstream O2 sensor which I replaced, the CEL was cleared, and I drove it 50 miles on the highway. Light stayed off for about a day.AWS today launched Amazon Honeycode, a no-code environment built around a spreadsheet-like interface that is a bit of a detour for Amazon’s cloud service. Typically, after all, AWS...I know that there are a few threads on here mentioning the P0420 code. My jeep is a 2012 JKU with 65k miles on the clock. The CEL has been on for about 6 months. I took it back to the dealer about a month ago for a recall and asked them to check the P0420 code that I read with my Scangauge II. Picked it up and they said that it just needed flashed.Jeep Cherokee P0420 Code Symptoms. The P0420 code in a Jeep Cherokee will often be thrown if one of your vehicle’s oxygen sensors is not functioning correctly. There are rarely drivability issues associated with P0420. For most people, the first sign that anything is wrong is the service engine soon light coming on.FansEdge coupons save you 65% during March 2023 summer sale. Use our Fansedge coupons and promo codes to save an average of $65% OFF. Free US shipping on order.. PCWorld’s coupon s...Te suministramos todo lo que necesitas saber sobre el código DTC P0420: ️ Descripción, ️ causas, ️ síntomas y ️ posibles soluciones.LEER SOLUCIÓN DEL CÓD...

To confirm it is an O2 sensor, you need to get a scanner and watch the O2 sensors in real time. If the sensor after the cat is displaying basically the same info as the sensor before the cat, the cat is toast. If the sensor after the cat is showing nothing, as in no voltage, the sensor is bad. A good sensor after the cat should show some ...Here's how to modify your car's oxygen sensor to get rid of a P0420 OBDII code, clear the check engine light and pass an emissions test.The P0420 code is thr...The code P0420 (Catalyst Efficiency Issue) has nothing to do with you filling up the gas tank, its a coincidence it came up when you had just filled up. The most common causes of this are a failing o2 sensor, failing catalytic converter or an exhaust leak. This is an older thread, you may not receive a response, and could be reviving an old thread.Code p0456 wrangler jeep P0420 tj wrangler 2012 jeep wrangler unlimited review and road test. Used 2012 Jeep Wrangler Unlimited Call of Duty MW3 For Sale ($27,995 2012 jeep wrangler unlimited altitude edition Jeep wrangler unlimited sahara door 4x4 suv front edition review altitude sport vs prices used silver cars trucks canada angular.P0420 P0430 How to locate your BANK 1 or BANK 2 Cat Convertor, Here is the best way to find your bank 1 cat convertor. p0420 catalyst system efficiency bel...

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Jeep Patriot 2008 Engine Light - P0420 (code) Jump to Latest Follow 10K views 3 replies 3 participants last post by Terasec Sep 23, 2014. J. Jeepn_Creepn Discussion starter 5 posts · Joined 2014 Add to quote; Only show this user #1 · Sep 22, 2014. My engine lights keeps appearing and then dissapearing. ...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. When they see that the converter is not "cleaning" the exhaust enough to meet specs, …O2 p0420 code fix simulator jeep engine tj check light trouble converter catalytic'06-'18 jeep wrangler p0300 obd code: intermittent miss / misfire (dtc p0300) P0420 toyota prius trouble code top causesHow to fix jeep p0306 engine code in 3 minutes [2 diy methods / only $4.76].Google Authenticator can now sync single-use two-factor authentication codes to Google Accounts, for added convenience. Google Authenticator just got an update that should make it ...

Code P0420 means “Catalyst system efficiency below threshold (Bank 1).” Driving long-term with this code can cause engine and exhaust system damage. The most common cause of P0420 is a bad catalytic converter, but it can also be caused by other issues, such as a faulty oxygen sensor, a rich or lean running condition, or misfires.P0420 OBD-II Trouble Code: P0420 Catalyst System Efficiency Below Threshold (Bank 1) P0305 OBD-II Trouble Code: P0305 Cylinder 5 Five Misfire Detected ... Jeep Wagoneer Forum 3K+ members. Home. Forums. Model Specific Jeep Discussions. Wrangler TJ (Model years 1997-2006) ...JEEP CHEROKEE CODE P0420 CATALYTIC CONVER CODE FIX, ENGINE LIGHT ONIf you have Jeep Cherokee and you have Code P0420 and your engine light is on we will expl...P0420 code indicates that signal from downstream sensor is similar to signal from upstream sensor and cat is not providing increased O2 content of exhaust stream as expected. P0138 is high voltage code from downstream O2 sensor, usually indicates that sensor isn't putting out normal varying voltage signal based on O2 content of exhaust stream ...This page is meant to help you troubleshoot the Jeep Commander P0420 trouble code. It covers the P0420 code's meaning, symptoms, causes, and possible …O2 sensor part numbers? Filled my '12JKUR (80,000 miles) with ARCO gas, which is supposed to be Top Tier, and a few miles down the road, check engine light comes on; codes were P0430 (cat insufficiency) and P0158 sensor 2/2 (driver's side?). Took it into dealer and they said replace all 4 cat converters and all 4 sensors for $3600!What is the Cost to Diagnose the Code? Labor: 1.0. The cost to diagnose the P1404 Jeep code is 1.0 hour of labor. The diagnosis time and labor rates at auto repair shops vary depending on the location, make and model of the vehicle, and even the engine type. Most auto repair shops charge between $75 and $150 per hour.Ok yall here is my question. I have 2x now gotten a P0420 code and 1x a P0432 code. My OBD readings for both Bank 1 sensors are fluctuating between .08 v and .800v. Both Bank 2 sensors are also fluctuating like both Bank 1. Any ideas if its just my 02's post cat are bad or if its something...2008 jeep Patriot p0420 and p0139. Jump to Latest Follow ... My girl bought a used car recently and she had two codes p0420 and p0139. I guess the guy that had it probably cleared the codes before selling it to her i bet. I changed both up and downstream sensors and i knew it would be a roll of the dice doing this without confirming they were bad.P2096. Post Catalyst Fuel Trim System Too Lean Bank 1. P0133. O2 Sensor Circuit Slow Response Bank 1 Sensor 1. P0420. Catalyst System Efficiency Below Threshold Bank 1. Jeep Commander Limited 2007, V8. Like. Sort by Oldest first.Re: 1997 Jeep Grand Cherokee with P0420 code Post by jeff compton » Fri Dec 04, 2009 12:37 am Bosch 02's are junk, the heater elements are the wrong resistance value and often won't satisfy the monitor requirements, that being said most aftermarket converters wont either, as well there should be software update for your jeep,Just bought a 2008 Jeep Patriot Limited. It is the first Jeep I have owned and am pretty happy with it. I bought it with 170,000km on it, and it has the check engine light registering code P0420 (catalytic converter issue). I am going to try two things: First, I am going to replace the O2 sensors. Second, I was thinking of trying to clean the ...

New code just popped up: P0420 "catalyst system efficiency below threshold bank 1" 1997 Jeep Grand Cherokee, v8, 5.2liter, 4wd, 'limited', t-case swapped to NP242. ... A forum community dedicated to all jeep owners and enthusiasts. Come join the discussion about performance, engine swaps, modifications, classifieds, troubleshooting, maintenance ...

P0401 is a very common OBDII trouble code that’ll pop up in the Jeep Wrangler. It has to do with the emissions system and stands for Exhaust Gas Recirculation (EGR)→ Insufficient Flow. ... Related: P0420 Jeep Wrangler. Jeep Wrangler P0401 Symptoms. Most of the time, there will not be symptoms associated with P0401 in the …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.What It Is: The P0456 code in your Jeep Wrangler, identified using an OBDII scanner, indicates a small leak in the evaporative emission control system.It is often associated with codes like P0420, P0441, and P0440. Impact: P0456 typically doesn't pose an immediate threat to your Wrangler's driveability, but addressing any service engine soon light promptly is always wise.338. Location. Washington DC. Mar 27, 2021. #1. I will try to make this short and sweet. Last week I filled up my 2000 Jeep TJ and minutes later the check engine light came on. The code that came back was P0420 Bank 1. The check engine light remained on all week until I got gas today and, boom, the check engine light is gone.Hey all. So, im getting the 'ol P0420 and P0430 codes. Going to replace the CAT with a new DAVICO one, but how do I figure out what caused it to fail in the first place? Already replaced 3 out of 4 of the o2 sensors (Bank 1, #1 & 2 and Bank 2, #2) hoping that it would be just that, but it wasnt.The causes of code P0302 are listed below: Spark plug failure. Spark plug wire failure. The coil pack is not working. The fuel injector is faulty, unclean, or clogged. Cylinder compression is low. Excessive rotor button wear and tear. Engine speed sensor (crankshaft/camshaft) failure. Valve damaged or burnt.HELP!! P0420, P0153 codes. I have a 2007 Wrangler, we replaced the complete exhaust system from the manifold back about 18 months ago and replaced all the O2 sensors, Recently my check engine light came on, upon checking with a code reader, code P0153 O2 sensor 2/1 Slow Response came on. I cleared the code, thinking it wasn't possible for the ...

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O2 sensor part numbers? Filled my '12JKUR (80,000 miles) with ARCO gas, which is supposed to be Top Tier, and a few miles down the road, check engine light comes on; codes were P0430 (cat insufficiency) and P0158 sensor 2/2 (driver's side?). Took it into dealer and they said replace all 4 cat converters and all 4 sensors for $3600!Hello, I have a 2007 Jeep Patriot. My car currently had the check engine light one and I got it check and it said P0420, which i was told is very expensive to replace. ... but still lazy enough to cause a P0420. That code is just the computer saying that the downstream sensor is moving more than it should in comparison to the upstream sensor.Generally, a P0430 means the same thing as a P0420 DTC. The only difference is that the latter shows the problem exists in bank 1. Most four-cylinder and all inline engines have a single bank. So for a proper ... Since there are several causes of a P0430 code on Jeep Grand Cherokee and other car models, there are also several probable solutions ...P0420 bank engine catalyst efficiency check code light system threshold below dtc limited diagnosis Q&a: jeep dtc p0463, p0158, p0420 30 Oct 2023 Ff80 4ce3 afbc Catalytic converter jeep cherokee grand location 1998 engine sensor bank o2 check light bolts gif 1993 replace cherokeeforum ww2 zj Engine check light p0420 fixHow 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...I bought a 2007 Jeep Wrangler with 109k miles on Dec 31, 2019 from a small dealer. On Jan 1, 2020 the check engine light came on. The code is P0420 and P0430. I took it to a reputable Jeep mechanic and he said the catalytic converters had recently been replaced. He recommended I replace the O2 sensors with new factory ones, which I did.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.P0420 Code. My wife's 2015 2.4 4x4 threw a P0420 code which seems to indicate either a bad cat or bad o2 sensor. I was going to throw some sensors at it ($16 on RockAuto) but then I realized the federal emissions warranty on the cat is 80k 8 years and we bought it May 2015 and have 74k on it. So we are right on the tail end of the warranty ...In this video, you'll learn the causes and solutions of the P0420 code. The causes of the P0420 code are a bad catalytic converter, an ECM update, an exhaust... ….

P0420 code indicates that signal from downstream sensor is similar to signal from upstream sensor and cat is not providing increased O2 content of exhaust stream as expected. P0138 is high voltage code from downstream O2 sensor, usually indicates that sensor isn't putting out normal varying voltage signal based on O2 content of exhaust stream ...Jun 14, 2020 · Tech Notes. The P0440 code means that the control module has detected a leak in the Evaporative Emission (EVAP). Loose fuel tank filler cap is the most common cause that triggers the P0440 code. ⚠ Check if your Jeep have Safety Recalls. Hotline Archive With OEM Direct diagrams, components, TSBs, and R&R procedures Number: 345123 Vehicle Application: 2002 Liberty 3.7 Customer Concern: Has a check engine light on with codes P0137, and P0138 for the 1/2 O2 sensor voltage high and low. Average Reported Mileage: 70183 Tests/Procedures: 1. Check the scan data for O2 sensor voltages. The sensor should be switching from 2.5 to 3.5 volts.262 posts · Joined 2015. #13 · Mar 25, 2021. I get these pre cat failure codes after the wife drives the keep for a bit. (‘00 Cali TJ) After I run it around a couple days, the cats seem to clean out and the codes self clear. I think she lugs it around in high gear and my consistent 3k rpm shifts build enough heat to burn the carbon out.Model Specific Jeep Discussions. Wrangler TJ (Model years 1997-2006) TJ Technical Discussion. p0420 code. Jump to Latest Follow 21 - 25 of 25 Posts. 1 2. DoubleOught · Registered. Joined Feb 21, 2014 · 1,209 Posts #21 · Jun 28, 2014. Only show this user. Also agree with you that every 99 4.0 I have seen also had the old style manifolds. ...The Jeep 4.0-liter engine uses a cast iron block and cylinder head. It comes in both an inline-6 and inline-4 cylinder version and the specifications vary, depending on the vehicle...Recently my jeep has been kicking a P0420 code "Catalyst System Efficency Below Threshold (Bank 1)". ... I still need to fine tune some exhaust adjustments but this took care of my P0420 code for a year. Fast forward to August 2018 and driving around town and bing, P0430 code. This is now bank 2.New to the forum I have a 2014 Grand Cherokee Ecodiesel with 128,000 on it I recently got the P0420 light. Has anyone got this code and have any fix for it? Save Share. Like. ... Jeep Garage is where you can talk about all your favorite jeeps including the Cherokee, Liberty and Grand Cherokee.Thanks, please give me a moment to pull the information. P1064-CYLINDER 4 OIL SUPPLY SOLENOID VALVE STUCK. P0420-CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD BANK 1. These two codes could be a seperated issue. For the p1064 the possible causes. LOW ENGINE OIL. INCORRECT OIL FILTER THAT DOES NOT MEET OEM SPECIFICATIONS. Jeep p0420 code, Jun 14, 2020 · Tech Notes. The P0440 code means that the control module has detected a leak in the Evaporative Emission (EVAP). Loose fuel tank filler cap is the most common cause that triggers the P0440 code. ⚠ Check if your Jeep have Safety Recalls. , Thanks, please give me a moment to pull the information. P1064-CYLINDER 4 OIL SUPPLY SOLENOID VALVE STUCK. P0420-CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD BANK 1. These two codes could be a seperated issue. For the p1064 the possible causes. LOW ENGINE OIL. INCORRECT OIL FILTER THAT DOES NOT MEET OEM SPECIFICATIONS., 210. Reaction score. 3. Location. Lilburn. I had to disconnect the driver side cat and crossover exhaust pipe (one piece on 2003 Liberty's after 2/2/2003) to change the transmission. I re-installed the original starter with 173k miles when re-assembling the vehicle. Upon startup I got the P0420 cat efficiency code at about 30-50 mile intervals., If the voltage of the downstream oxygen sensor decreases, and begins to fluctuate like the upstream oxygen sensor, it means that the oxygen levels are too high and the Power Control Module will then store the P0420 trouble code and can be the source of the hard to start issue you’re experiencing., CODE P0420 DODGE DART, CHRYSLER 200, JEEP CHEROKEE COMPASS RENEGADE. Code p0420 dodge dart, chrysler 200, jeep cherokee compass renegade Ff80 4ce3 afbc Jeep p0420 wrangler. 2004 jeep wrangler unlimited p0420 code. P0420 tj wrangler .. Check Details Check Details. I have a 2012 jeep wrangler 2.6l I'm getting codes p0300 & p2308, Srry. Check ..., p0420のエンジンコードを自宅で修理できますか? p0420エンジンコードは自宅で確かに修理できます。ただし、問題があります。変更を進める前に、問題を正しく診断することが絶対に必要です。問題の原因に応じて、次のことが必要になる場合があります。, I have a 2005 Jeep Grand Cherokee and I have codes P0420 and P2096. Submitted: 10 months ago. Category: Jeep. Show More. Show Less. Ask Your Own Jeep Question. Share this conversation. Answered in 2 minutes by: 6/6/2023., I really wanna become a diagnostics master, so any and all help is very much appreciated. I replaced the fuel pump ($300) in my WJ last year, and it ended up being the ECU which prompted me to stop being a parts cannon master. I checked the FAQ which listed all OBD2 codes and searched the forum for live data info but couldn't find anything., bush1355. 11 posts · Joined 2009. #3 · Jan 9, 2021. I have had this code P0420 catalyst efficiency for a few years now. Originally cobe was accompanied by 02 sensor code. (no P code to recall, but P code present) Have had only P0420 since. Dealer said new converter needed ($1300), but running fine in mileage & performance., To diagnose the P0432 Jeep code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour., In this video, you'll learn the causes and solutions of the P0420 code. The causes of the P0420 code are a bad catalytic converter, an ECM update, an exhaust..., Uh oh, it's the dreaded P0420 (or P0430)… This Ford Taurus gave me the opportunity to discuss catalytic converter testing, as well as a chance to demonstrate..., O2 p0420 code fix simulator jeep engine tj check light trouble converter catalytic'06-'18 jeep wrangler p0300 obd code: intermittent miss / misfire (dtc p0300) P0420 toyota prius trouble code top causesHow to fix jeep p0306 engine code in 3 minutes [2 diy methods / only $4.76]., Step 1 - Resolve Engine Trouble Codes. The first step is to resolve any other codes that may have come up in addition to the P0420; especially troublesome is the P0300 series of cylinder misfire codes. A P0300 code could be related to something in the ignition (spark plug or coil), the fuel injector, compression or fuel contamination., Labor: 1.0. To diagnose the P0688 Jeep code, it typically requires 1.0 hour of labor. The specific diagnosis time and labor rates at auto repair shops can differ based on factors such as the location, make and model of the vehicle, and even the engine type. It is common for most auto repair shops to charge between $75 and $150 per hour., I have a 2005 Jeep Grand Cherokee and I have codes P0420 and P2096. Submitted: 10 months ago. Category: Jeep. Show More. Show Less. Ask Your Own Jeep Question. Share this conversation. Answered in 2 minutes by: 6/6/2023., HELP!! P0420, P0153 codes. I have a 2007 Wrangler, we replaced the complete exhaust system from the manifold back about 18 months ago and replaced all the O2 sensors, Recently my check engine light came on, upon checking with a code reader, code P0153 O2 sensor 2/1 Slow Response came on. I cleared the code, thinking it wasn't possible for the ..., Code p0335Jeep p0420 wrangler Another p0420 / p0430 thread.P0431 - warm up catalyst efficiency bank 2 - jeep wrangler tj 6. 2004 jeep wrangler unlimited p0420 code.Diagnose and fix jeep wrangler p0457 Code p04202014 jeep wrangler unlimited p0420-m. 2014 Jeep Wrangler Unlimited P0420-M - Beckley WV - YouTube. Check Details. How to fix ..., P0420 jeep tj 2000 wrangler 2017 jeep wrangler p0306Wrangler jeep p0304 code misfire trouble relatively obd2 includes common vehicle any 46e0 7ad4 8cf5P0420 jeep. Diagnose and fix jeep wrangler p0457Jeep wrangler tj p0456 p0455 trouble evac repair codes Wrangler p0456 evap obdiiGot code p0325 on 2009 jeep wrangler x, where is the knock sensor ..., Check engine light code P0456 means the evaporative emission control system leak (small). Find out how to fix it in this article! ... Popular Engine Codes P0420 P0172 P00171 P0128 P0300 P0456 P0430 P0442 P0455 P0113. ... Toyota 4Runner vs. Jeep Grand Cherokee | The Best Model Year For Every Budget, 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. , A faulty or deteriorated catalytic converter. Oxygen sensor malfunction. An exhaust leak before the catalytic converter. Engine misfire. Fuel injector issues. It is …, Te suministramos todo lo que necesitas saber sobre el código DTC P0420: ️ Descripción, ️ causas, ️ síntomas y ️ posibles soluciones.LEER SOLUCIÓN DEL CÓD..., What Does The P0420 Code Mean? The P0420 code indicates that the Engine Control Module (ECM) has identified a decline in the efficiency of the catalytic converter on Bank 1. This could be attributed to a malfunctioning catalyst or potentially be a false alarm triggered by a defective O2 sensor., Engine code P0420 means the catalyst is not working to maximum efficiency. Converter may be failing or rear O2 sensor is reading wrong. ... Lost code for Jeep CRD limited Radio. 2000 Jeep Cherokee Limited 4-Door 4WD-Maintenance & Repair. Code P0420 2 Answers. After replacing catalyst converter check engine light lit. Scanner shows code P0420 ..., This page is meant to help you troubleshoot the Jeep Liberty 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. ... The bank 1 version of this code is P0420. Jeep Liberty P0430: Symptoms., Code P0420. Jump to Latest Follow 13K views 5 replies 3 ... West Virginia Jeep Club member, A malfunctioning catalytic converter is the usual suspect for a P0420 code. Some more possible causes are: Damage to or leakage from the exhaust manifold ; Damage or leaking in the exhaust pipe ; Engine misfire ; Contamination of catalytic converter oil ; Sensor for engine coolant temperature that isn't working properly, I have a 2001 wrangler with about 175K. My CEL came on yesterday and I'm getting a P0420 code "catalyst system efficiency below threshold." In the last year or so, I've had intermittent problems starting it on cold mornings -- basically need to give it gas while turning the ignition and then keep my foot on the gas to idle for a while or it will stall., Codes P0420 and P0420. Hi all! I am new to the forum. I have a 2011 GC Limited, V6, 3.7L, 160K Miles. A few months ago, the check engine light came on with the codes P0420 and P0430. Since then, I have replaced all 4 O2 sensors and the gas cap (I heard that may be an issue too). I also stopped topping off when I get gas., P0420 Bank 1 and P0430 Bank 2* Codes on 2009 JKU. I have a 2009 JKU and am getting P0420 Bank 1 and P0430 Bank 2 (yes 2 not 1) codes. I have been doing some research and this seems like an odd combination - at least it is to me. She seems to be running good - has 129K miles. These are the only 2 codes present., In this video I replace the rear O2 sensor (bank 1) on a 2008 Jeep Grand Cherokee 3.7 V6. This vehicle has a trouble code P0420 stating the catalyst system e... , 2008 jeep Patriot p0420 and p0139. Jump to Latest Follow ... My girl bought a used car recently and she had two codes p0420 and p0139. I guess the guy that had it probably cleared the codes before selling it to her i bet. I changed both up and downstream sensors and i knew it would be a roll of the dice doing this without confirming they were bad.