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P0420 code changed o2 sensors check egine light still comes on 2000 chevy express 1500 4.3L V6

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If the sensor didn't fix it check the wiring to make sure it's not broken anywhere...Also if you bought the sensor at a large parts outlet it could be defective...not likely but possible...

Posted on Feb 03, 2010

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My 2005 chevy equinox keeps showing problem code P0420 How do I fix this problem?


0 2 sensor near the catalytic converter or

replace the catalytic converter

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.

Read more at: https://www.obd-codes.com/p0420
Copyright OBD-Codes.com

https://www.obd-codes.com/p0420

Feb 03, 2017 | Cars & Trucks

2 Answers

What means catalyst Efficiency below normal


      Got it scanned and it's P0420: Catalyst efficiency below thresholdbank 1. They said it could be a bad catalytic converter or oxygen sensor. I borrowed a scanner and tried to measure the oxygen sensor readings over time.Sep 8, 2011

      civic - Check Engine code P0420 Catalyst efficiency below ...

      mechanics.stackexchange.com/.../check-engine-code-p0420-catalyst-efficie...
    Feedback

    P0420 Error Code: Catalyst System Efficiency Below ...

    www.obd-codes.com/p0420
    P0420 OBD-II Trouble Code. Technical Description. Catalyst System Efficiency Below Threshold (Bank 1). What does that mean? This diagnostic trouble code ...

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Jan 26, 2016 | Cars & Trucks

1 Answer

Replaced catalyst converter, both sensors and still have code P0420 what's the problem


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.



Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Aug 24, 2012 | 2002 Honda Civic

1 Answer

2001 Toyota Camry - check engine light on - code p0420 - took to mechanic and he just hooked up code scanner and gave p0420 code - without checking anything else he said rear O2 sensor needs to be...


Hello: Code 420 normally indicates a catalytic converter is operating below 60% efficiency. You need to take your car to another shop and request a COMPLETE diagnosis not a dart board guess.

Sep 13, 2011 | 2001 Toyota Camry

1 Answer

Have a p0420 code on 2000 celica should i replace o2 sensors or cat


The catalytic convertermag-glass_10x10.gif 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.

Feb 17, 2011 | 2000 Toyota Celica

1 Answer

Have a 4.3 v6. code p0420 . it was running realy bad so, I changed the o2 sensor bank1 and did a complete tune up including dist., rotor, wires, plugs, filters oil, cleaned maf and intake. I cleared the...


That code is a converter preformance code. You shoul'd have a qualified Tech. with a good scanner take a look at it. There are several things that could set it.

Jan 20, 2011 | 2003 Chevrolet Express

3 Answers

Pulled code p0420 on 99 chevy astro, 2wd, v6


from what i am finding the code means o2 sensors. they recommend replacing them and if this does not work than replacing the cat converter

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.

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 soloutions

Some suggested steps for troubleshooting a P0420 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.


thank you for choosing fixya and please do not forget to comment and rate on your experience.

Aug 20, 2009 | 1999 Chevrolet Astro

3 Answers

Have a 2003 Chevy Impala. Check engine light remains on. Scan showed O2 sensor. Could it be a vaccum leak?


Bank 1 is the rear O2 sensor, but experience says to change both. The front one is right behind the engine in the middle of the engine compartment. The rear O2 sensor is on the top of the exhaust pipe, just behind the catalytic converter. But the same code that shows it is the O2 sensor (which is P0420), is the same code for the catalytic converter, or a vacuum leak. Make sure if you do change the catalytic converter, ensure that the new one is OBD-2 compliant. And the vacuum leak could possibly come from the manifold gasket. Let me know what the problem was!

Mar 11, 2009 | 2003 Chevrolet Impala

2 Answers

2000 Mazda Miata, check engine light comes on. Code PO420


I HAVE A 2000 MAZDA MIATA AND IT IS BRINGING UP A CODE PO421, CAN YOU TELL ME WHAT THAT IS

Dec 15, 2008 | 2000 Mazda MX-5 Miata

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