P0420 bad under body catalytic converter 2003 Nissan Altima
Hello, I have my car that had many issues that I was able to repair myself. For example, fouled spark plugs and ignition coil packs because of a bad valve cover. I replaced it and car is running well. Then I get code p0420, I sometimes get excessive smoke from tail pipe during some cold day startups. I took to mechanic for diagnostics to find which catalytic converter is bad. From my understand my car has two of them, one accessible from the engine bay and the other under the car. If I remember right the mechanic found the rear one has gone bad. I will call to make sure it's that one. Bu
Experienced mechanics share their insights in answering this question :
Hi there – you are correct that there are 2 catalytic converters on your vehicle; one (sometimes called a pre-catalyst) that is part of the exhaust manifold, and a 2nd converter further "downstream" in the exhuast system. It is the 2nd converter that has oxygen sensors before and after, and usually triggers an "under-efficiency" issue. There is, however, a Nissan Recall (Recall 03V084000) on the "pre-converter" that is part of the exhaust manifold, and may be replaced under that Recall. If you are unsure if this repair has been done, check with your Nissan dealer. If the 2nd converter does need to be replaced, I recommend a catalytic converter replacement performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.
How to Identify and Fix Common car Problems ?
Our sources include academic articles, blog posts, and personal essays from experienced mechanics :
Code P0420 indicates that the catalytic converter is not functioning efficiently, therefore increasing the output of harmful pollutants by the vehicle.
The most common cause of a P0420 code is a faulty catalytic converter. The following are some other potential causes: Exhaust manifold damage or leakage.
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.
If you`re experiencing a slow engine ability, lowered acceleration, a smell of rotten eggs or sulfur from the exhaust, dark exhaust smoke, or extreme heat coming from under the vehicle, they are symptoms of a clogged Catalytic Converter, and it should get replaced soon.
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.
Can a bad O2 sensor cause a P0420 code? Yes. A typical catalyst monitor uses the signal from the downstream oxygen sensor to determine catalyst efficiency, and the signal from the upstream sensor is a reference point. As such, failure of either the upstream or downstream oxygen sensor can cause code P0420 to set.
Yes. Bad spark plugs can cause a P0420 code because when one or more spark plugs are faulty, they are not able to ignite the air and fuel mixture in the combustion chamber so the unburnt mixture, along with the Nitrogen Oxide and Carbon Monoxide from the combustion chamber will go into the catalytic converter.
Problems with the ignition system, fuel system, air intake, and misfires can damage a catalytic converter if they are not addressed quickly. These components are most the common causes of the P0420 trouble code.
Can spark plugs cause P0420? P0420 denotes either an issue with the oxygen sensors or a fault with the catalytic converter that reduces its efficiency. So, yes, it`s possible that a defective plug is enabling unburned fuel to enter the cat and causing damage to it over time.
Since catalytic converters have limited oxygen storage capacity, the rear O2 sensor will detect the excessive oxygen and generate a converter efficiency code. Leaks in the exhaust system can affect oxygen storage in the converter and lead to improper O2 sensor readings, affecting the air/fuel ratio (AFR) balance.
Common P0420/P0421 Symptoms
Other items that could be causing multiple trouble codes to appear with the 420/421 codes are: Bad Oxygen Sensors (either upstream or down) Engine Rich / Lean condition. Bad MAP or MAF sensor.
The p0420 code means that the catalytic converter is below threshold and is not functioning correctly. This code comes up when the catalytic converter can no longer burn off any fuel in the exhaust system.
The code P0420 means that the catalytic converter is below threshold and cannot burn off any emissions in the exhaust stream. The O2 sensors have pickup this fault and put the engine into limp mode. As for the vehicle not moving, the exhaust may be plugged up causing the engine to not breathe properly.
A common emissions code seen in the field, a P0420 trouble code indicates that the catalytic converter isn`t functioning efficiently. To work at peak efficiency, the emissions or feed gases entering the catalytic converter need to be perfectly balanced and not excessively elevated.
A P0420 code indicates a malfuction in your Catalytic Converter Efficiency Test due to a failing catalytic converter. However, it can also mean something else such as; Bad O2 sensor (either upstream or downstream), either the heater circuit or a stuck value. An exhaust leak which may fool the O2 sensors.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
P0420 bad under body catalytic converter 2003 Nissan Altima
ANSWER : Hi there – you are correct that there are 2 catalytic converters on your vehicle; one (sometimes called a pre-catalyst) that is part of the exhaust manifold, and a 2nd converter further "downstream" in the exhuast system. It is the 2nd converter that has oxygen sensors before and after, and usually triggers an "under-efficiency" issue. There is, however, a Nissan Recall (Recall 03V084000) on the "pre-converter" that is part of the exhaust manifold, and may be replaced under that Recall. If you are unsure if this repair has been done, check with your Nissan dealer. If the 2nd converter does need to be replaced, I recommend a catalytic converter replacement performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, give you an accurate assessment of damage and cost estimate for repairs.
Read Full Q/A … : P0420 bad under body catalytic converter 2003 Nissan Altima
2004 Nissan Altima- Won’t move when the code reads p0420 on the scanner. Did my transmission go? Is it my catalytic converter like code said?
ANSWER : Hi there. The code P0420 means that the catalytic converter is below threshold and cannot burn off any emissions in the exhaust stream. The O2 sensors have pickup this fault and put the engine into limp mode. As for the vehicle not moving, the exhaust may be plugged up causing the engine to not breathe properly. Put the vehicle in drive and set the parking brake. Fully step on the gas pedal to the floor and have someone feel the exhaust pipe. If there is very little pressure coming out of the pipe, then the catalytic converter has plugged up and needs replaced. If the pressure is normal, then the computer may have locked the transmission out of the drive cycle. If you need further assistance with your vehicle not moving due to the code p0420, then seek out a professional, such as one from Your Mechanic, to help you.
Read Full Q/A … : P0420 bad under body catalytic converter 2003 Nissan Altima
Bad catalytic converter and white smoke from tire
ANSWER : Hello. This does sound like a problem related to the catalytic converter being faulty. The smoke from the driver’s side front wheel could be caused by the front driver side caliper locking up. This may make the wheel difficult to spin and may also be causing the white smoke. When the catalytic converter is causing drivability issues, it may get very hot to the point that it turns red. The extreme heat could cause the brake fluid to boil, which may also make the front wheel lock up. I would suggest that you have a certified technician, like one from YourMechanic, come and inspect the brake system as well as the catalytic converter.
Read Full Q/A … : P0420 bad under body catalytic converter 2003 Nissan Altima
Changed catalytic converter, no lights on dashboard, but codes for catalytic converter & O2 sensor still remain
ANSWER : Hi there, thanks for writing in. I am not sure why you changed your catalytic converter. Assuming you had a P0420 code, replacing the catalytic converter should of resolved that code. The codes originally stored need to be cleared. The fact your check engine light remains off tells me, you may have fixed the problem. Try disconnecting the negative battery terminal for at least 2 minutes, reconnect. Start and drive the vehicle for 10-15 miles. Re-check for codes. If a code returns on the first drive cycle (pending code), a problem still exists. The check engine light should come back on (the next drive cycle) if, the fault is recognized by the computer. An exhaust leak before the oxygen sensor will cause O2 sensor and catalytic converter codes. If you are having trouble identifying the fault, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.
Read Full Q/A … : P0420 bad under body catalytic converter 2003 Nissan Altima
Hi Mr. Nicholas: Engine light of my Accord Lx 2010 comes on. I want to be sure the problem is with the catalytic converter or O2 s
ANSWER : Hi there. In short, yes – it is highly probable that the check engine light is not 100% caused by the catalytic converter. Most OBD-II trouble codes related to this system are actually caused by O2 sensor failure, electrical harness failure to O2 and the catalytic converter or other emissions systems. On your Honda, there is one catalytic converter, that is comprised of a few individual sections. When it it replaced however, it is replaced as a single unit. In most cases, when a Honda dealership tells you that the catalytic converter is the source, 80% of the time they are correct. I would recommend reading this article and asking yourself if you are experiencing more than 50% of these are occurring.
Read Full Q/A … : P0420 bad under body catalytic converter 2003 Nissan Altima
Is it bad to drive a car with a bad throttle body??
ANSWER : Hey there. This may not immediately affect your car’s engine. However, it will continue to cause intermittent misfires and will gradually get worse. This may also have an impact on other parts as well since the missing cylinder will still be receiving fuel. This fuel only has one of two places it could go: either out of the exhaust as raw unburnt fuel causing damage to the catalytic converter (which may also trigger more fault codes such as the O2 sensor), OR this fuel will end up down in the oil with the oil which causes the oil to break down. When this happens, the oil loses its effectiveness on protecting other vital engine parts. For more help, I would recommend having an expert from YourMechanic come to your home to diagnose and repair the misfire for you.
Read Full Q/A … : P0420 bad under body catalytic converter 2003 Nissan Altima
My catalytic converter is rattling and there is smoke coming from my car. Is the catalytic converter faulty?
ANSWER : It is possible the catalytic converter got hot enough to fail on the last trip you took before this started. No pressure from the exhaust is a good sign that the car can’t breath. This may be because it cannot get enough air or because it cannot exhale.
The only way to confirm definitively is to perform all of the tests the previous mechanic performed to confirm the diagnosis. There are a few other sensors that may cause similar issues, but the scan for diagnostic troubleshooting codes would have alerted you at that point. A muffler shop will be able to confirm if the cat is bad. You can knock on it and see if you hear a rattle of some sort. This is a sign the filter inside has become heated, brittle, and broken off on the inside.
I recommend having a certified mechanic, such as one from YourMechanic, come to you to determine if the catalytic converter needs to be replaced and why smoke is coming from the car.
Read Full Q/A … : P0420 bad under body catalytic converter 2003 Nissan Altima
What would happen if the wrong catalytic converter was installed in my 2001 Toyota Camry
ANSWER : Hello. The wrong converter will cause your check engine light to come on and will cause you to not pass emissions. It can also cause some performance and efficiency issues over time. There are specific converters built for all vehicles and that is what needs to be used, especially in California. You need to take it back to the shop that installed the wrong one as it is against emission regulations to install the wrong converter in California.
Read Full Q/A … : P0420 bad under body catalytic converter 2003 Nissan Altima
