New exhaust no cst converters chanch sensors twice problem stay p0420

Did you reset the code?

Try some of this to clean the fouling in the rest of the system,

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The P0420 code means that the catalytic converter efficiency is below threshold. Since there are two oxygen sensors, above and after the catalytic converter, they together generate signals which are used to monitor the efficiency. However, if the catalytic converter is bad, the sensor after the converter will generate steady results, without any fluctuations.
You can replace the catalytic converter to overcome this problem. However, there are chances of the P0420 code to come up if there is any leak in the exhaust or the downstream o2 sensor (after the converter) is bad. Ideally, before spending on cat, you should try replacing the downstream sensor, which you can buy at low price from online stores like oxygensensorworld.com and also inspect for any small leaks in the exhaust system. Since the converter can cost you more, think of replacing it only if needed.

Hi there:
The possible causes of this code are: exhaust leak between the exhaust manifold and converter, downstream O2 sensor wiring damaged due to coming in contact with exhaust pipe, or failed converter.


Check for any exhaust leaks and repair as necessary. Check wiring harness at O2 sensor and if damaged repair or replace. Keep in mind that catalytic converter have a 8yr/80,000 mile federal emissions warranty, so if you have less than 80,000 miles this will be covered undered the warranty and would need to be replaced by dealership.


We strongly recommend that if you need to replace the catalytic converter that you replace it with an OEM unit. Second choice would be a high-quality replacement part. There are many stories in our forums where folks replaced the cat with a cheaper aftermarket one only to have the code return shortly thereafter.



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P0420 = Bank 1 catalyst system efficiency below threshold. This DTC (Diagnostic Trouble Code) is set when the O2 downstream sensor indicates/measures the amount of hydrocarbons/oxygen present in the exhaust after it passes through the converter. When this sensor detects exhaust gasses identical/near identical to the upstream O2 Sensor (the actual gasses at the exhaust port - before the converter), it will set this 'efficiency below threshold' code. The catalyst has failed to 'convert' the exhaust gasses to CO2 + Water.

A code P0420 may mean that one or more of the following has happened:

• Leaded fuel was used where unleaded was called for
• An oxygen sensor is not reading (functioning) properly
• The engine coolant temperature sensor is not working properly
• Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
• Retarded spark timing
• The oxygen sensors in front and behind the converter are reporting too similar of readings

Possible SolutionsSome suggested steps for troubleshooting a P0420 error code include:

• Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
• Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
• Inspect the downstream heated oxygen sensor (HO2), replace if necessary
• Replace the catalytic converter

Code p0303 means one cyliner is misfireing. Check spark plugs and wiring cables. If one cylinder isn't working good that could be the possible couse for the first code P0420 and all other engine problems.

a p0420--means one of the following has happened. an oxygen sensor is not reading properly, the engine coolant sensor is not working properly, damaged or leaking exhaust manifold /catalytic converter/ exhaust pipe, retarded spark timing, the oxygen sensors in front and back of converter are reporting too similar of readings. A P0420 - P0430 are pointing at the catalytic converter, and changing the Oxygen Sensors would be the major choice. good-luck!!

The code PO420 you have is Catalyst System efficiency is below threshold bank one. Usually replacing the O2 sensor that's the front most in the exhaust system will cure your problem,

Your Check Engine light is on and you find a P0420 code for a catalytic converter fault. Does that really mean your converter has reached the end of the road and needs to be replaced? A new converter can cost $600 to $1000 or more if a new car dealer or repair shop does the job, or maybe half that amount if you do it yourself. It's an expensive fix that may or may not be necessary. The problem, in most cases, is an emissions issue, not a performance issue that affects the way the engine runs.

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 theexhaust manifold reflects the condition of the exhaust gases as they exit the engine. The downstream O2 sensor in or behind the catalytic converter reflects the condition of the exhaust after it passes through he converter.

The catalytic converter is like an after-burner. It oxidizes (burns) any residual fuel vapors (unburned hydrocarbons or HC) in the exhaust. It also burns any carbon monoxide (CO) in the exhaust. The exhaust must meet federal emission standards, and if a problem exists that causes emissions to exceed the federal limits by 150%, the OBD II system is supposed to catch the fault, set a code and turn on the Check Engine light.

Thanks

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

What does that mean? 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. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.


Symptoms You will likely not notice any drivability problems, although there may be symptoms.
Causes A code P0420 may mean that one or more of the following has happened:

• Leaded fuel was used where unleaded was called for
• An oxygen sensor is not reading (functioning) properly
• The engine coolant temperature sensor is not working properly
• Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
• Retarded spark timing
• The oxygen sensors in front and behind the converter are reporting too similar of readings

Possible Solutions Need a catalytic converter? Visit our catalytic converter shopping area for the lowest price on your replacement converter!
Some suggested steps for troubleshooting a P0420 error code include:

• Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
• Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
• Inspect the downstream heated oxygen sensor (HO2), replace if necessary
• Replace the catalytic converter

One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.

Yes the front O2 sensor(the one before the cat) could be lazy and cause this also.

The code PO420 you have is Catalyst System efficiency is below threshold bank one. Usually replacing the O2 sensor that's the front most in the exhaust system will cure your problem,

Your Check Engine light is on and you find a P0420 code for a catalytic converter fault. Does that really mean your converter has reached the end of the road and needs to be replaced? A new converter can cost $600 to $1000 or more if a new car dealer or repair shop does the job, or maybe half that amount if you do it yourself. It's an expensive fix that may or may not be necessary. The problem, in most cases, is an emissions issue, not a performance issue that affects the way the engine runs.

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 theexhaust manifold reflects the condition of the exhaust gases as they exit the engine. The downstream O2 sensor in or behind the catalytic converter reflects the condition of the exhaust after it passes through he converter.

The catalytic converter is like an after-burner. It oxidizes (burns) any residual fuel vapors (unburned hydrocarbons or HC) in the exhaust. It also burns any carbon monoxide (CO) in the exhaust. The exhaust must meet federal emission standards, and if a problem exists that causes emissions to exceed the federal limits by 150%, the OBD II system is supposed to catch the fault, set a code and turn on the Check Engine light.

Thanks