Jeep p0420 code

Jan 25, 2024 · Understanding the P0420 Code in Your Jeep Liberty. The P0420 code is a common diagnostic trouble code that indicates a problem with the catalytic converter in your Jeep Liberty. In this section, we will explain what the code means and its potential causes. Possible Causes for a P0420 Code in a Jeep Liberty. There are several factors that can ...

2007 Jeep Liberty 3.7 code p0420 catalyst efficiency bank 1. Most the most common cause for the code? Answered in 1 minute by: Jeep Mechanic: Pete. Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay. The most common cause is a restriction in the ...Jeep Grand Cherokee & Commander Forums. WK Grand Cherokee & XK Commander Forum. code P0420? 1450 Views 0 Replies 1 Participant Last post by tednelson83, May 7, 2007. T. tednelson83 Discussion Starter · May 7, 2007. Only show this user. has anyone ever gotten this code? was there an easy fix OTHER than replacing the cat? ...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.NOTE: Take note that while the cods listed below are not strictly related to P0420 - " Catalyst System Efficiency Below Threshold (Bank 1)", these codes often appear with P0420. P0421 - "Warm Up Catalyst Efficiency Below Threshold (Bank 1)". P0422 - "Main Catalyst Efficiency Below Threshold (Bank 1)". P0423 - "Heated ...Code P0430 means that the downstream oxygen sensor from the catalytic converter on bank 2 detects the cat isn’t operating to efficiency standards, based on factory specifications. The P0430 trouble code is considered generic, meaning it occurs on vehicles of any type and model. The P0430 shows a problem with the emissions system.P0420 – Catalyst System Efficiency Below Threshold (Bank1) is an emission/exhaust-related trouble code reporting inefficient operation of your CAT (catalytic converter). It is important not just to confirm a bad catalytic converter, but also to diagnose why it went bad to prevent damage to a newly installed one as they can cost up to $2000.By rasmataz, Certified 2CarPros Master Technician. A code P0300 may mean that one or more of the following has happened: Faulty spark plugs or wires. Faulty coil (pack) Faulty oxygen sensor (s) Faulty fuel injector (s) Burned exhaust valve. Faulty catalytic converter (s) Stuck/blocked EGR valve / passages.

12470 posts · Joined 2019. #9 · Dec 3, 2020. P0430 is a Catalyst Efficiency Bank 2 code on a Jeep. "The eyes are useless, when the mind is blind". "Life begins at the end of your comfort zone". "If you're running with the squirrels, …May 24, 2019 · 102 posts · Joined 2013. #1 · May 24, 2019. I have been dealing with a frustrating P0420 code. Maybe once a tank (for me that is like a little over a week or so). and then I have to be driving with low RPMs in the 2000-2500 with little if any throttle. It seams to be more likely at half a tank Or less. Engine is most often at full operating ... Mar 13, 2023 · NOTE: Take note that while the cods listed below are not strictly related to P0420 – “ Catalyst System Efficiency Below Threshold (Bank 1)”, these codes often appear with P0420. P0421 – “Warm Up Catalyst Efficiency Below Threshold (Bank 1)”. P0422 – “Main Catalyst Efficiency Below Threshold (Bank 1)”. P0423 – “Heated ... 2014- 3.6L just got p0520 and P06DE. My pressure reads 100 psi and doesn't move. I was going to replace oil pressure switch but a friend said I probably need a new oil pump. I bought it used with 38 k on it and it now has 61k on it. Regular oil changes with Castrol Edge synthetic. Any thoughts would be appreciated.Code P0420. Jump to Latest Follow ... West Virginia Jeep Club member ... i had some o2 sensor heater codes pop in my 04 cleared it out twice now, about 8k miles later, never returned, i think my jeep just fixes itself sometimes because it knows im too lazy to do it . 2004 Grand Cherokee Laredo 4.096XJ 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 O2 sensors at the time ...

2011 Jeep Compass P0420 Code. A few weeks ago my car started throwing a P0420 (Catalytic converter below threshold). I had the code cleared, it then came back on and proceeded to go back off on its own a week later. It returned a few days ago so now I am trying to figure out if this is a catalytic converter issue or an O2 sensor issue.When left unattended, a P0456 Jeep code can lead to compounded performance issues and huge repair expenses. That said, it is best to pick up on its symptoms early on. P0456 Jeep code symptoms include: A triggered Check Engine Light. Starting difficulties. Fuel odors in your cabin.The P0420 Code indicates that your car’s computer has discovered an issue with the Bank 1 catalytic converter. Bank 1 represents the engine’s top cylinder, which is located on the engine’s side. Bank 2 runs in the opposite direction of the engine. How Much Does P0420 Repair Cost?P0420 code catalyst efficiency threshold below fix Ford fiesta p0420 code Jeep p0420 Jeep P0420 - Meaning, Causes, Symptoms, & Fixes - FIXD Best OBD2 Scanner Sensor jeep bank cherokee grand 2005 p2096 code o2 where dodge engine converter limited neon exhaust side check gif justanswer Jeep cherokee code p0420 catalytic conver code fix, engine ...NOTE: Take note that while the cods listed below are not strictly related to P0420 – “ Catalyst System Efficiency Below Threshold (Bank 1)”, these codes often appear with P0420. P0421 – “Warm Up Catalyst Efficiency Below Threshold (Bank 1)”. P0422 – “Main Catalyst Efficiency Below Threshold (Bank 1)”. P0423 – “Heated ...

Alterations express cranberry.

Síntomas del código OBD2 P0420. Los síntomas de un código de avería P0420 pueden ser:. Pérdida de potencia del motor: El vehículo puede experimentar una disminución en su rendimiento y tener dificultades para acelerar. Aumento en el consumo de combustible: El automóvil puede consumir más combustible de lo normal debido a un problema en el sistema catalizador.A P0420 code is set when the upstream sensor and the downstream oxygen sensor sense the catalytic converter is not doing its job. Basically, the amount of oxygen going into the converter is not being burned, and it detects it through the downstream sensor. Oxygen is the key here. Modern Engine Management Systems leave a little bit of extra ...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].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...Causes. A code P0430 may mean that one or more of the following has happened: The catalytic converter is no longer functioning properly. An oxygen sensor is not reading (functioning) properly. There is an exhaust leak. Possible Solutions. First, inspect for exhaust leaks.Overall probably the biggest mistake vehicles owners make when they have a P0420 code is to simply replace an oxygen sensor (H02S). It is important to do proper diagnosis so you're not wasting money replacing parts unnecessarily ... Find answers to all your Jeep Patriot technical questions. Show Less . Full Forum Listing. Explore Our Forums.

However, if the P0420 code is the only trouble code - or if the other codes are all P042X codes - the likelihood of a failed catalytic converter is much higher. Likely Causes For P0420 Trouble Code In A Toyota. Leaded fuel in an unleaded system will nearly always trigger this, given the differing properties of leaded fuel combustion and exhaustEND OF SPECIAL NOTES. OBD II fault code P0420 is a generic trouble code that is defined as, P0420 - "Catalytic converter system, Bank 1 - Efficiency Below Threshold", and is set when the PCM (Powertrain Control Module) detects that the efficiency of the catalytic converter on Bank 1 has fallen below a minimum allowable threshold.Jeep Liberty P0420 Code Symptoms. The P0420 code in a Jeep Liberty 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.Here are some steps to fix a P0420 code Honda Accord. First, remove the O2 sensor and pour 4-6 ounces of seafoam into the opening, replace the sensor, and leave it overnight. Reset the code and then continue driving. Increase the gap between the oxygen sensor and the converter using a spark plug non-fowler.Here are some steps to fix a P0420 code Honda Accord. First, remove the O2 sensor and pour 4-6 ounces of seafoam into the opening, replace the sensor, and leave it overnight. Reset the code and then continue driving. Increase the gap between the oxygen sensor and the converter using a spark plug non-fowler.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.Do you occasionally get code P0420 - catalytic converter low efficiency? This $3 electrical circuit may fix the problem permanently by electrically smoothin...Confirm it's a P0420 code. Before we move into the details on fixing the P0420 code command is very important to make sure that the problem exists in the 1st place. Therefore, the first step here is to use an OBDII tool scanner and connected it to the vehicle to check whether the P0420 code is there or not.Code-switching involves not only shifting the way we speak, but also the the way you behave and express yourself. There are many reasons you may do it. If you speak multiple langua...The P0420 code in a Jeep Patriot will often be thrown if one of your vehicle’s oxygen sensors is not functioning correctly. There are rarely drivability issues associated …

Learn how you can improve your code quality in an instant following 3 simple rules that we cal Receive Stories from @gdenn Get free API security automated scan in minutes

P0420 is a diagnostic trouble code that relates to the catalytic converter on bank 1 in Dodge vehicles. When this code appears, it suggests that there is a malfunction with the catalytic converter, specifically on bank 1. The catalytic converter is responsible for reducing harmful emissions from the vehicle's exhaust system.Causes. Possible causes of OBD code P0402 Jeep. A code P0402 Jeep most likely means one or more of the following has happened: The DPFE (differential pressure) sensor is faulty and needs to be replaced There is a blockage in the EGR (most likely carbon buildup) The EGR valve is faulty The EGR valve may not be opening due to a lack of vaccuum.Nov 5, 2011 · 7386 posts · Joined 2008. #1 · Nov 5, 2011. Hey guys, CEL came on yesterday and i did the three time ignition check with my key and the code came up a p0420.. Looked it up online and people were saying its my catalayic converter. So, considering that I just got a new exhaust not too long ago, would it be my o2 sensor in the cat? Summary. DTC P0520 stands for "Engine Oil Pressure Sensor/Switch "A" Circuit.". This is logged when the PCM detects problems with the oil pressure sensor, oil pressure switch, or the oil pressure in general. Code P0520 is usually triggered because of faulty oil pressure sensors, bad circuitry, and low oil pressure.Code P0420:02 Sensor Upstream Replacement:2015 Jeep Patriot Sport FWD 2.0L 4 Cyl.Lubricant:Permatex Dielectric Tune-Up Greasea. Autozone Link - https://www.a...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 readings, a ...Jeep Grand Cherokee & Commander Forums. ZJ Grand Cherokee Forum. Another P0420 CEL code Problem..... Jump to Latest Follow 1 - 14 of 14 Posts ...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 ...The first step is to check the engine light to see if the P0420 code is illuminated. If the engine light is on, then the next step is to check for any other codes that may be accompanying the P0420 code. Once any other codes have been addressed, the next step is to inspect the exhaust system for any leaks or blockages.

Kellie pickler net worth.

Crawfish festival syracuse 2023.

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.The P0420 code is a generic OBD-II code that indicates a problem with the catalytic converter in a vehicle. In the case of the Ford Fiesta, this code specifically relates to a malfunction in the catalytic converter's efficiency. The P0420 code is an important indicator of potential emissions-related issues in a Ford Fiesta.The first step is to check the engine light to see if the P0420 code is illuminated. If the engine light is on, then the next step is to check for any other codes that may be accompanying the P0420 code. Once any other codes have been addressed, the next step is to inspect the exhaust system for any leaks or blockages.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.Been getting the p0420 code and if deleted it comes back in about 2 weeks so ---- I stop and get a gallon of laquer thinner and put it in the tank--- ... I talked to the Jeep mechanic changing the engine in my Jeep about the cats. The cats were giving off a fine residue which, due to the close proximity of the cats to the exhuast valves, the ...4653 posts · Joined 2006. #3 · May 20, 2015. not sure of NJ inspection requirements. in NY can only have 1 emission code, if you have 2 it fails, p420 usually triggers other emmisions codes, I have had p0420 on for about 3 yrs. past 2 inspections what I did was use heavy duty emmissions cleaner as instructed, they go by different names like ...55 posts · Joined 2015. #7 · Mar 17, 2015. P0394-CAMSHAFT POSITION SENSOR INTERMITTENT - BANK 2 SENSOR 2. I believe this is the left bank intake camshaft position sensor. Sensor is on top of the valve cover towards rear.=====Claim your FREE engine code eraser 👉 https://free.nonda.co 👈=====Engine Code P0420 Saving Repair Parts:C...That P0420 codes is one of the most unambiguous of all the diagnostic trouble codes. That code is thrown when the upstream and downstream O2 sensors both have the same "switching frequency." That means that the cat is doing very little to change the exhaust gas composition. In other words, the cat needs to be replaced. ….

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.Catalyst System Efficiency Below Threshold (Bank 1) is the meaning of the P0420 code. This code indicates that Catalyst System Efficiency (Bank 2) is below the threshold (P0430). The number one cylinder is located on the bank 1 side of the engine. In Bank 2, you will find the opposite side of the engine. P0420 and P0430 both showed up …Decode over 200 OBD2 trouble codes by number, description, symptoms and fixes. Vehicle-specific check engine light diagnostics for common DTCs P0420, P0301, P0171. Learn causes, locate your OBD port, get estimates and clear codes. In-depth DTC guides turn cryptic codes into confident car & truck repairs.Developing apps normally needs experienced programmers who are familiar with development. However, these low-code and no-code apps change the paradigm. Receive Stories from @elinex...Mar 29, 2023 · B. bardwell02. 72 posts · Joined 2011. #2 · Mar 30, 2023. Hi; I have never had this code on my Jeep, but interestingly enough it's popped up on one of my other vehicles, an Audi RS4 (I believe it's P0430 - catalyst efficiency on that one!) Common cause on those cars is a bad O2 sensor, not the cat itself going bad. =====Claim your FREE engine code eraser 👉 https://free.nonda.co 👈=====Engine Code P0420 Saving Repair Parts:C...If you’re planning a trip to explore the breathtaking beauty of the great outdoors, there’s no better way to do it than with Pink Jeep Tours. One of the easiest and most effective ...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. Jeep p0420 code, HI, Ok, there are several possible causes. P0420 is for the main stage catalytic converter on bank 1 and P0430 is for the warm up catalytic converter on bank 1. IT is VERY rare for both to fail at the same time unless there is an underlying cause such as running rich and raw fuel getting into the converters and burning them up., TechCrunch will not tolerate any type of harassment of attendees, including the following but not limited to: Because of the following but not limited to: As an attendee, you are e..., JEEP COMPASS RENEGADE CODE P0111 P0112 P0113 P0114 ENGINE LIGHT ON FIX. Check Details. CODE P0420 DODGE DART, CHRYSLER 200, JEEP CHEROKEE COMPASS RENEGADE. Check Details. JEEP COMPASS RENEGADE 2.4 CODE P0037, P0038, P0054 ENGINE LIGHT ON FIX. Check Details. Jeep Compass 1,6D 120hp FWD Longitude - Lease-today.eu, MeanGreenZJ. 1708 posts · Joined 2011. #9 · Feb 2, 2012. My guess is that the P0430 code is triggered by the P2098 code. Which points to a failed 02 sensor or circuit, exhaust leak or mechanical issues. Or as said above a flash update issue., Since you don't have a cat the PCM will always think its not working and throw a code. There are devices you can buy to plug in where the O2 sensor was to trick the computer in thinking the cat is working, but I have never used on., Sep 30, 2018 · The most common fix for P0420 in the Jeep Renegade is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Renegade 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 Jeep Renegade: 1. Check for Other Codes. , 4653 posts · Joined 2006. #3 · May 20, 2015. not sure of NJ inspection requirements. in NY can only have 1 emission code, if you have 2 it fails, p420 usually triggers other emmisions codes, I have had p0420 on for about 3 yrs. past 2 inspections what I did was use heavy duty emmissions cleaner as instructed, they go by different names like ..., October 03, 2023 -. P0420 stands for a code that signals the "Catalyst System Low Efficiency" issue and is a relatively common occurrence, especially with cars that are only driven over short distances. As the catalytic converter plays a vital role in reducing emissions and maintaining the overall performance of your vehicle, it is important to ..., Ford Code P0420: This code indicates a problem with the catalytic converter system in a Ford vehicle. It specifically refers to a low efficiency of the catalytic converter in Bank 1, which is the side of the engine where cylinder 1 is located. When the catalytic converter fails to reduce emissions effectively, it triggers the check engine light ..., 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..., Then set torque to display the O2 sensor outputs. You should then be able to see the levels cycling. Next step is to swap the offending sensors, (downstream usually), left/right & see if the fault stays on the one side, (bad cat), or swaps over, (bad sensor, much cheaper). I had this & it was a bad cat in the end., 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..., Dec 11, 2019 · P0420 Code 2007 3.8L JK. A couple of months ago the P0420 was thrown. I reset it with the BlueDevil OBD II tool. But after a series of trips it reappears. The catalytic converter had been replaced in 2017 and the vehicle only has about 5000 more miles on it since then. I replaced all four Oxygen sensors again to be sure but still the same problem. , JEEP COMPASS RENEGADE CODE P0420 CATALYST EFFICIENCYIf you Jeep Compass or Renegade and you have engine light on and code P0420 we will show what usually cau..., If you've been looking to learn how to code, we can help you get started. Here are 4.5 lessons on the basics and extra resources to keep you going. If you've been looking to learn ..., Code Tech Notes. As the code description implies, the P0420 code means that the vehicle's Powertrain Control Module (PCM) has detected that the Three-way Catalyst Converter is not working properly (it is not as efficient as the factory expects). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases, the Three-way ..., May 30, 2012 · That P0420 codes is one of the most unambiguous of all the diagnostic trouble codes. That code is thrown when the upstream and downstream O2 sensors both have the same "switching frequency." That means that the cat is doing very little to change the exhaust gas composition. In other words, the cat needs to be replaced. , 7386 posts · Joined 2008. #1 · Nov 5, 2011. Hey guys, CEL came on yesterday and i did the three time ignition check with my key and the code came up a p0420.. Looked it up online and people were saying its my catalayic converter. So, considering that I just got a new exhaust not too long ago, would it be my o2 sensor in the cat?, The P0455 Jeep code occurs when the PCM detects a large EVAP leak. Symptoms include an illuminated CEL, subpar engine performance, stalling, and excessive exhaust smoke (among others). A malfunctioning gas cap or a defective emissions control system component can cause the fault code. However, the list does not end there., Take off the cover and remove the fuse for the controller. Install new fuse with the correct amperage. Reattach the negative battery terminal. Start the ignition to see if the code clears. If the code isn't clear, you'll need to take your car in for further diagnostics., 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., Summary. DTC P0520 stands for "Engine Oil Pressure Sensor/Switch "A" Circuit.". This is logged when the PCM detects problems with the oil pressure sensor, oil pressure switch, or the oil pressure in general. Code P0520 is usually triggered because of faulty oil pressure sensors, bad circuitry, and low oil pressure., 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., 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., Code Tech Notes. As the code description implies, the P0420 code means that the vehicle's Powertrain Control Module (PCM) has detected that the Three-way Catalyst Converter is not working properly (it is not as efficient as the factory expects). Replacing the oxygen (O2) sensors may sometimes fix the code, but in most cases, the Three-way ..., 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., I own a 15' patriot 4wd latitude , this is my wife's daily driver we bought it off the dealer 4 years ago aprox, I've done maintenance throughout the years , now I had that p0420 code pop out. I've had it about for almost 2 years now , and it's bothering me ., I started getting the P0420 code about 8 months ago. No other symptoms. 2 days ago, I heard the chime like there was a problem. Check codes and there was another P0420. ... Join our community to discuss the Jeep Patriot & Jeep Compass. Find answers to all your Jeep Patriot technical questions. Show Less . Full Forum Listing., If you are a car owner, it is likely that you have encountered the dreaded check engine light at some point. One of the most common trouble codes that many drivers come across is c..., =====Claim your FREE engine code eraser 👉 https://free.nonda.co 👈=====Engine Code JEEP P0038 Saving Repair ..., Code P0430 means that the downstream oxygen sensor from the catalytic converter on bank 2 detects the cat isn’t operating to efficiency standards, based on factory specifications. The P0430 trouble code is considered generic, meaning it occurs on vehicles of any type and model. The P0430 shows a problem with the emissions system., 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., A P0420 diagnostic trouble code is a "generic" fault code that is set when the Onboard Diagnostic II (OBD II) system sees a drop in converter efficiency. The OBD II system monitors catalyst efficiency by comparing the switching activity of the upstream and downstream oxygen sensors in the exhaust. The upstream O2 sensor in the exhaust manifold ...