P0420 dodge bank 1 location

Repair Information for P0420 Dodge code. Learn what Catalyst System Efficiency Bank 1 means, location and how to repair? The Engine Control Module (ECM) monitors the switching frequency ratio of heated oxygen sensors 1 (front O2 sensor) and heated oxygen sensors 2 (rear O2

Code P0420 Description. The Engine Control Module (ECM) uses sensors mounted in front of and behind the Three-Way Catalytic Converter (TWC) to monitor its efficiency. The first sensor, the air-fuel ratio sensor, sends pre-catalyst information to the ECM. The second sensor, the heated oxygen sensor, sends post-catalyst information to the ECM.A P0420 fault code displayed on an OBD2 reader would suggest that the car that it is plugged into is experiencing a problem with its catalytic converter. More specifically it has detected that the oxygen level at the sensor after the catalytic converter is too high. Modern cars have oxygen sensors at various points along the route that air (and ...Causes. Diagnosis. Dodge Ram P0420 Quick Info Table. Dodge Ram 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 truck: P0420: Catalyst System Efficiency Below Threshold (Bank 1) Catalyst System Efficiency.Jan 27, 2021 · This article will therefore deal with code P0420 as it applies specifically to GM vehicles. OBD II fault code P0420 is a generic trouble code that is defined as “Catalytic converter system, bank 1 – efficiency below threshold” and is set when the PCM (Powertrain Control Module) detects a condition in which the efficiency of the catalytic ... 117K views 5 years ago. 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 …October 08, 2022. The code P0420 - Catalyst Efficiency Below Threshold (Bank 1) means that there is a problem with the catalytic converter of the Bank 1. The code P0430 …A vehicle’s (bank 2, sensor 1) O2 sensor will be located ahead or upstream of the catalytic converter on the bank which corresponds to the engine’s second cylinder. This is due to the fact that bank 2 is representative of an engine’s #2 cylinder, while sensor 1 serves as an upstream designation. Example DTC: Code P0154, Code P0175.

Interpreting the P0420 Code. If the O2 sensors detect similar results, then something is not right. The values of oxygen have to be different upstream and downstream from the converter.29175 posts · Joined 2007. #2 · Feb 11, 2019. P0420 = Catalytic converter system, bank 1 - efficiency below threshold. Possible causes; Catalytic converter, wiring, HO2S 2. The 4.0 is backward from convention. Piston 1 (Bank 1) is on the passenger side of the 4.0. O2 sensor 1 is the closest to the engine (pre-CAT) O2 sensor 2 is the farther ... 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. By using fine platinum and gold meshes to filter exhaust ... P0420- Catalytic Converter - Bank 1. I got this reading at advanced auto and then called my mechanic and told me the code is pretty straight forward and that is the problem. He said O2 sensors would throw there own code and some may say that there going bad but you'll only end up with the same code in the end. I was going to do the 5 minute fix ...INDCWBY Discussion starter. 77 posts · Joined 2007. #1 · Apr 7, 2013. I'm getting a P0420 Code Catalyst Efficiency Below Threshold (Bank 1) on my 06 Toyota Camry that has 140K on it. I replaced both O2 sensors. I cleared out the code and ran for 2 days. I was on the highway and decided to push the car by going faster than 80mph and … 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. By using fine platinum and gold meshes to filter exhaust ... Searching for a new bank can present challenges, especially if you have moved to a new location. Chances are, you might be able to use your existing bank for most purposes, but acc...

May 23, 2011 · P0420- Catalytic Converter - Bank 1. I got this reading at advanced auto and then called my mechanic and told me the code is pretty straight forward and that is the problem. He said O2 sensors would throw there own code and some may say that there going bad but you'll only end up with the same code in the end. I was going to do the 5 minute fix ... P0420 Diagnostic Code: Catalyst System Efficiency is Low (Bank 1) By: Dustin Porreca • Updated: Jan 6, 2024 One of the most common catalytic converter codes your vehicle will throw at you is the P0420 (not to be mistaken with trouble code P0430 ).Causes. A code P0420 may mean that one or more of the following has happened: Leaded fuel was used where unleaded was called for (unlikely) A damaged or failed oxygen / O2 sensor. Downstream oxygen sensor (HO2S) wiring damaged or connected improperly. The engine coolant temperature sensor is not working properly.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. This page is meant to help you troubleshoot the Chevy HHR P0420 trouble code. It covers the P0420 code's meaning, symptoms, causes, and possible solutions. ...

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Ford Explorer P0420 Code Symptoms. The P0420 code in a Ford Explorer 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.Unlock your vehicle's secrets with our comprehensive guide on the P0420 code. Get expert insights on understanding, diagnosing, and resolving this common issue. ... Catalyst System Efficiency Below Threshold (Bank 1) By Pedro Gomez. Updated on September 30, 2023. ... One is located before the CAT converter, and one is on each …Feb 22, 2015 · On my 2012 journey, MIL just came on, run OBD-II scan tool and what I get:""""" 2/21/2015 12:45:52 Dodge Journey 2012 Error#P0420 Catalyst System Efficiency Below Threshold (Bank 1) Freeze Frame for DTC P0420 Fuel System Status Bank One Closed Loop Fuel System Status Bank Two Closed Loop Calculat... P0420: Catalyst System Efficiency Below Threshold; P0421: ... while the downstream sensor is located after your catalytic converter, and it’s there to monitor exactly how your converter is performing – or simply put, is it doing it’s job. ... Was does system too lean bank 1 and bank 2 mean? Read More . Trouble Code P0451: EVAP Emission ...I have read a lot about the code and from what I read the O2 is a cheap start that may fix it. Read that cat can be 95% efficient and throw this code. But cat could be bad. Also read about using o2 simulator from O2 Simulator, Angled O2 Simulator clears p0420 / p0430 check engine light But it be a cheap fix vs a new cat.Operating at 1 locations. Chase Bank has 2 offices in Alameda, California. Find Chase Bank Alameda branch locations, hours of operation, phone numbers and driving …

Downstream – The downstream oxygen sensor’s (after the exhaust exits the catalytic converter) primary function is to verify the catalytic converter is doing its job. Often, an oxygen sensor is the cause of P0420. When an oxygen sensor has failed, it can cause a false reading and trigger this code in your car.Web Code P0420 Dodge Tech Notes. Check if this fits your 2012 dodge grand caravan. Web have p0420 code on a 2014 dodge grand caravan that states bank1. Web catalytic converter price: Web Table Of Contents. Web dodge > 2012 > grand caravan > 3.6l v6 > exhaust & emission > catalytic converter. Web you will need to got 10, 12mm sockets and ...Here’s a good P0420 diagnostic order for the Chrysler Sebring: 1. Check for Other Codes. The first thing you want to do when trying to fix P0420 in the Sebring 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.John Clark. This is just not true. The P0420 code is the one code that almost always means exactly what it says. Yes, one should check the functionality of the A/F sensors and the rear O2 sensor but just due to what the computer needs to see in order to set a P0420 or P0430 code it usually is NOT the sensors.Web Code P0420 Dodge Tech Notes. Check if this fits your 2012 dodge grand caravan. Web have p0420 code on a 2014 dodge grand caravan that states bank1. Web catalytic converter price: Web Table Of Contents. Web dodge > 2012 > grand caravan > 3.6l v6 > exhaust & emission > catalytic converter. Web you will need to got 10, 12mm sockets and ...Many factors can cause the car computer to register DTC P0420 on Toyota or any car model. This makes it challenging to diagnose and fix the problem. Engine running rich or lean. Malfunctioning upstream or downstream oxygen sensor. Leaking fuel injectors. Lousy catalytic converter. Lousy engine coolant temp sensor.How To Diagnose Trouble Code P0420: Catalyst Efficiency Below Threshold (Bank 1). TEST 1: Checking For a Broken Catalytic Converter. TEST 2: Checking The Output Of The Rear Oxygen Sensor. TEST 3: Manually Inducing A Lean Condition. TEST 4: Manually Inducing a Rich Condition. Where To Buy The O2 Sensor And Save $$$.October 08, 2022. The code P0420 - Catalyst Efficiency Below Threshold (Bank 1) means that there is a problem with the catalytic converter of the Bank 1. The code P0430 …

How To Diagnose Trouble Code P0420: Catalyst Efficiency Below Threshold (Bank 1). TEST 1: Checking For a Broken Catalytic Converter. TEST 2: Checking The Output Of The Rear Oxygen Sensor. TEST 3: Manually Inducing A Lean Condition. TEST 4: Manually Inducing a Rich Condition. Where To Buy The O2 Sensor And Save $$$.

Even slight variations in the air/fuel mixture will cause the converter temperature to rise significantly. The “Catalytic Converter Efficiency” Diagnostic Trouble Codes (DTCs) P0420 and P0430, are among the top 10 DTCs technicians face. And while the description might imply a failed converter, odds are the ultimate fault lies somewhere …Hyundai Accent 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 Accent’s exhaust contains hydrocarbons, carbon …Labor: 1.0. To diagnose the P0420 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. 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. The Bank of America website features a Locations link at the top of each page allowing users to find branch and ATM locations. The user enters a ZIP code, address or city and state...911 posts · Joined 2011. #3 · Jan 5, 2013. :agree: Yep, bank one is driver's side. Cylinder 1 is on front driver's side, Cylinder 2 is on front passenger side. Bob. SOLD: Highly modded '03 KJ Liberty Renegade. - Current Jeeps '06 XK Hemi Limited - OME HD Springs/Bilstein shocks, AiRaid CAI, Billet Technology catch can, SuperChips tuner, RHR ...If the P0420 code is combined with other codes, try fixing the other codes first. The code is detected when - Three way catalytic converter Bank 1 does not operate properly. - Three way catalyst converter Bank 1 does not have enough oxygen storage capacity.Bank 1 is the bank closest to the firewall on this engine. The code is for the converter as you know. There are a few possible causes for the converter code to appear. Here is some more info on the code for you. P0420 DODGE - Catalyst System Efficiency Bank 1.The most common fix for P0420 in the Nissan Titan is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Titan 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 Nissan Titan: 1. Check for Other Codes.Labor: 1.0. To diagnose the P0420 Nissan 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.

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I go through a diagnostic checklist for P0420. 1) No exhaust leaks (even small ones)ahead of or near the downstream O2 sensors. No physical damage to the exhaust system. 2)No misfires (can kill a cat fast) 3)Air Fuel and O2 sensors can respond with "full range" readings.Nov 30, 2018 · The most common fix for P0420 in the Dodge Charger is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Charger 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 Dodge Charger: 1. Check for Other Codes. The most common fix for P0420 in the Dodge Magnum is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Magnum 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 Dodge Magnum: 1. Check for Other Codes.The most common fix for P0420 in the Dodge Magnum is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Magnum 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 Dodge Magnum: 1. Check for Other Codes.Web Code P0420 Dodge Tech Notes. Check if this fits your 2012 dodge grand caravan. Web have p0420 code on a 2014 dodge grand caravan that states bank1. Web catalytic converter price: Web Table Of Contents. Web dodge > 2012 > grand caravan > 3.6l v6 > exhaust & emission > catalytic converter. Web you will need to got 10, 12mm …Catalytic converters don't last forever. In this video, we diagnose a P0420 on a Toyota Camry with over 330,000 miles! Enjoy!Sep 13, 2012 · The firing order is 1-6-5-4-3-2. The left bank is on the drivers side (3.7L). Bank 1 is on the drivers side of the 3.7. Bank 2 is the passenger side (3.7L). Sensor 1 is the upstream sensor before the catalytic converter. The R/T uses the 4.0L engine, and meder24's statement above is correct for the 4.0. 2007. Engine. 5.7 Hemi. I've got an 07 1500 5.7 QC 4x4. She's got roughly 181k miles on her. For about a year now I've had an intermittent cel for P0420. I've done a spark plug change, ran system cleaner, reset ecm, used an infrared thermometer and live data feed to try to diagnose it. Both infared and the LD show the cats to be operating at ...Part 2 How to replace a catalytic Convertor and O2 Sensor P0430 P0420 on Bank 2...The check engine light was on with P0340.. P0420 catalyst system efficiency...Nov 30, 2018 · The most common fix for P0420 in the Dodge Caliber is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Caliber 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 Dodge Caliber: 1. Check for Other Codes. ….

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. This page is meant to help you troubleshoot the Chevy HHR P0420 trouble code. It covers the P0420 code's meaning, symptoms, causes, and possible solutions. ...309. 43K views 1 year ago. How to fix a Dodge with a P0420 Code, "Catalyst System Efficiency Below Threshold (Bank 1)." Cataclean 120007 on Amazon: https://amzn.to/3EkiF4n ...more.Woodforest National Bank has over 700 branches for patrons to visit. The branches are scattered across the southern, eastern, and central part of the United States. To find the clo...I go through a diagnostic checklist for P0420. 1) No exhaust leaks (even small ones)ahead of or near the downstream O2 sensors. No physical damage to the exhaust system. 2)No misfires (can kill a cat fast) 3)Air Fuel and O2 sensors can respond with "full range" readings.Intermittently the check engine light will come on when the vehicle is warm usually in stop and go traffic or during slow manuevers. Plugging in an OBDII device it indicates a code and says "Catalyst System Efficiency Below Threshold (Bank 1)" I think it was a code P0420.The most common fix for P0420 in the Dodge Magnum is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Magnum 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 Dodge Magnum: 1. Check for Other Codes.#p0420 #p0430 #catalyticconvertercodes #badcat #autel #motoragetrainingThe “Catalytic Converter Efficiency” codes, P0420 and P0430, are among the top 10 DTCs...Hyundai Accent 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 Accent’s exhaust contains hydrocarbons, carbon … P0420 dodge bank 1 location, Honda. In Honda vehicles, the P0420 code is not uncommon. Common culprits include deteriorating catalytic converters and oxygen sensors. Regular maintenance and prompt repairs can help resolve the issue efficiently. Ford. Ford vehicles may also experience the P0420 code. Exhaust leaks, failing catalytic converters, and …, WHERE IS BANK 1 BANK 2 ON DODGE CHARGER, WHAT IS BANK 1 BANK 2 Dodge Parts here: https://amzn.to/3PeiPNx More Specific Parts Bellow If you have Dodge Charg..., The P0420 engine code indicates the catalyst system efficiency is below the threshold (Bank 1). A P0420 code indicates a problem with the catalytic …, South Indian Bank, one of the leading private sector banks in India, has been serving customers for over nine decades. With a strong network of branches spread across the country, ..., Causes. A code P0420 may mean that one or more of the following has happened: Leaded fuel was used where unleaded was called for (unlikely) A damaged or failed oxygen / O2 sensor. Downstream oxygen sensor (HO2S) wiring damaged or connected improperly. The engine coolant temperature sensor is not working properly., Feb 23, 2019 · DODGE JOURNEY WHICH SIDE IS BANK 1 BANK 2 3.6 V6 PENTASTARIf you need to know which side is Bank 1 and Bank 2 on 3.6 v6 Engine this is the right video for yo... , How to fix a Dodge with a P0428 Code, "Catalyst Temperature Sensor High Input (Bank 1 Sensor 1)."CataClean on Amazon: https://amzn.to/3rFr1Mr, Feb 16, 2019 ... Part 2 How to replace a catalytic Convertor and O2 Sensor P0430 P0420 on Bank 2...The check engine light was on with P0340., 1. Incorrect torque 2. Damage If a condition is found: Replace the B52B Heated Oxygen Sensor 2 or repair the condition as necessary. If no condition is found 1. Replace the exhaust front pipe and the warm up three-way catalytic converter. NOTE: A new converter with less than 100mi on it may set the P0420 DTC due to outgassing of …, P0420: Catalyst System Efficiency Below Threshold; P0421: ... while the downstream sensor is located after your catalytic converter, and it’s there to monitor exactly how your converter is performing – or simply put, is it doing it’s job. ... Was does system too lean bank 1 and bank 2 mean? Read More . Trouble Code P0451: EVAP Emission ..., Nov 30, 2018 · The most common fix for P0420 in the Dodge Caravan is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Caravan 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 Dodge Caravan: 1. Check for Other Codes. , Toyota Tundra P0420 Code Symptoms. The P0420 code in a Toyota Tundra will often be thrown if one of your truck’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., Jan 29, 2022 ... What's going on HEMI Gang  !! Can Ya Hemi back again with another video for you guys. This video shows how to change an oxygen ..., The most common fix for P0420 in the Chrysler 300 is a new catalytic converter, followed by an O2 sensor replacement. Before taking your 300 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 Chrysler 300: 1. Check for Other Codes., SmartAsset's experts review Regions Bank. We give an overview of all the bank's account offerings, rates and fees as well as branch locations. See if opening up an account with thi..., The most common fix for P0420 in the Dodge Dakota is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Dakota 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 Dodge Dakota: 1. Check for Other Codes., The P0420 code in Ford Focus specifically relates to the Bank 1 catalytic converter, which is the one located before the engine’s cylinder head. Symptoms of a P0420 code in Ford Focus When a Ford Focus experiences the P0420 code, several symptoms may occur., The P0420 code is a very popular one and that's why there's a site dedicated to that specific trouble code. If your car's check engine light is on, get that code read in case it's a P0420. A P0420 code is a trouble code on OBD-II equipped vehicles. All vehicles from 1996-newer sold in North America support this generic powertrain code., Dodge Grand Caravan Catalytic Converter Replacement (3.3 and 3.8 engine) Cut And WeldHow to replace catalytic converter assembly. Thanks For WatchingIf You F..., Repair Information for P0420 Dodge code. Learn what Catalyst System Efficiency Bank 1 means, location and how to repair? The Engine Control Module …, The most common fix for P0420 in the Dodge Avenger is a new catalytic converter, followed by an O2 sensor replacement. Before taking your Avenger 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 Dodge Avenger: 1. Check for Other Codes., SOURCE: location of bank 1 sensor 1 o2 sensor. Should be in the manifold on the back side closest to the firewall. SOURCE: 2005 dodge grand caravan getting code p0406. 3.3 engines has the egr valve with transducer.you have to replace the whole unit. code p0406 what its trying to tell you your egr valve circuit is short to ground.it has failed ., P0420 Possible Symptoms. P0420 is not always noticeable except the engine light/service engine soon warning light. Sometimes, you can feel the lack of power from the engine and decreased fuel economy. Engine Light ON (or Service Engine Soon Warning Light) Lack of power from the engine. Decreased fuel economy. Rotten egg or a sulfur smell., On these vehicles Honda used a wideband air fuel ratio sensor in the upstream sensor locations. Historically, the downstream sensors are just for checking for catalyst efficiency. ... P0420 is a bank 1 cat code (rear bank.) You said the internals came out of bank 2 cat, which if bad would trigger a P0430. Bank 1 is the rear bank and bank 2 is ..., P0420 - Catalyst System Efficiency Below Threshold (Bank 1) P0430 - Catalyst System Efficiency Below Threshold (Bank 2) The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate., Toyota Tundra P0420 Code Symptoms. The P0420 code in a Toyota Tundra will often be thrown if one of your truck’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., 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..., Web Code P0420 Dodge Tech Notes. Check if this fits your 2012 dodge grand caravan. Web have p0420 code on a 2014 dodge grand caravan that states bank1. Web catalytic converter price: Web Table Of Contents. Web dodge > 2012 > grand caravan > 3.6l v6 > exhaust & emission > catalytic converter. Web you will need to got 10, 12mm …, October 08, 2022. The code P0420 - Catalyst Efficiency Below Threshold (Bank 1) means that there is a problem with the catalytic converter of the Bank 1. The code P0430 means the same fault for the Bank 2 catalytic converter in an engine with two cylinder banks (e.g., V6 or V8). The catalytic converter or "cat" is a key component of the vehicle ..., Get ratings and reviews for the top 11 pest companies in Fort Dodge, IA. Helping you find the best pest companies for the job. Expert Advice On Improving Your Home All Projects Fea..., Dec 27, 2020 ... ... 1 SENSOR 1) - UPSTREAM - RIGHT - CLOSEST TO ... 2008-2020 3.6L Dodge Grand Caravan - Upstream and Downstream Oxygen Sensor Replacement (Bank 2)., 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 …, 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 ...