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I have a 2005 Chevy Malibu showing a diagnostic code of P0420. What could the problem be so I can fix it and clear the code.

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6ya6ya
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Posted on Jan 02, 2017

CMV9
  • 594 Answers

SOURCE: 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.


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Posted on Aug 20, 2009

motor1258
  • 6674 Answers

SOURCE: 1999 cougar diagnostic code p0430 and p0420

Failed or faulty oxygen sensor, or faulty catalytic converter. It's actually the oxygen sensor reading that the catalytic converter is not functioning properly & needs relacement. That's provided the oxygen sensor is not faulty, which personally, I'd go for that first.
Both would explain excessive fuel usage.

Posted on Jan 25, 2009

  • 35 Answers

SOURCE: 2002 chevy impala p0420 code.

here is a site that may help you with your po420 code http://www.aa1car.com/library/p0420_dtc.htm

Posted on Mar 04, 2009

  • 18 Answers

SOURCE: 2005 Toyota Camry check engine

go to autozone they will scan it no charge and do reset, give u possible causes and repairs, are u sure its not the oil change interval light,your owners manuel will tell u how to reset if thats the case

Posted on Mar 05, 2009

localwonder
  • 6784 Answers

SOURCE: Engine light came on. The dealership said it was diagnostic code P0420 and that it would cost @ $1,200.00 to repair. This seem pretty high. What is this diagnostic code about and is the repair rate

Hi, this code represents a Catalyst System Efficiency Below Threshold (Bank 1). and the repair, considering that it will be repaired by the dealership, seems to be in the normal cost range. The labor is what usually inflates the price when dealing with catalytic replacements.

You could probably get a better deal by taking it to a non dealership type of repair shop. This may cut at least 200 dollars of the original dealership quote.

Please rate and god bless:)

Posted on Apr 14, 2009

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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

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Hi Rabih,

I hate to tell you this, but it is time to stick your hands DEEP into your pockets and get ready to spend the big bucks! Diagnostic Trouble Codes (DTCs) P0420 and P0430 are "catalyst efficiency below threshold" codes. The ONLY way to fix them is to replace your catalytic converters. If you also have any other codes, you must fix these FIRST, otherwise you will only destroy new converters as well.

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I have a 1999 chevy malibu its 6 cylinders 3100 engine and i have the codes with me this aare the codes that i need 1.#p0420 2.#p0410 3.#p0305 4.#p0449


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2006 chevy cobalt(85000 miles) check engine light comes on and stays on. I am getting the check engine light code p0420. Engine seems to be running smoothly.


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

TSB Number: 3316 NHTSA Number: 10017210 TSB Date: n/a Date Added to File: October 27, 2005 Failing Component:Electrical System Summary:Diagnostic trouble code P0420 may set on low mileage vehicles, or shortly after catalytic converter replacement
TSB Number: 3316 NHTSA Number: 10017210 TSB Date: n/a Date Added to File: October 27, 2005 Failing Component:Electrical System Summary:Diagnostic trouble code P0420 may set on low mileage vehicles, or shortly after catalytic converter replacement
there is a service bulletin for this.

http://www-odi.nhtsa.dot.gov/cars/problems/tsb/results.cfm?start=1&SearchType=DrillDown&type=VEHICLE&year=2005&make=CHEVROLET&model=COBALT&vehtype=PC&typenum=1&component_id=0&summary=true

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05 Chevy Malibu P0420 code has set the check engine light.


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