Question about 2002 Honda Civic

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'02 civic engine code P0420. What does this mean?

Engine code comes up in my 'o2 civic coupe. My OBD11 scanner says code P0420 Generic Catalyst efficiency below threshold (Bank 1). Do you know what's wrong with my car?

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  • swipht25 Feb 20, 2009

    Ok. I replaced both 02 sensors last year, do you still think I should replace the pre cat 02 sensor?

  • swipht25 Feb 20, 2009

    Generic catalyst Efficiency below threshold (Bank 1). Would that be the front catalytic convertor that needs to be replaced?

  • Anonymous Feb 20, 2009

    2006 Honda Civic engine code P0420

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  • 28 Answers

It means your 02 sensor pre cat is not working or the cat is no longer any good start with the 02 sen its easy to do and cheaper than the cat

Posted on Feb 19, 2009

  • Breckon b Mar 04, 2009

    yah its the one closest to the motor on the exhaust system

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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...
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    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 ...

    P0420 Code Fix How Its Done Catalyst Efficiency Below ...

    ? 4:25
    https://www.youtube.com/watch?v=-c8090n1Ihs
    Jun 20, 2014 - Uploaded by ACE AUTOS UK
    Here is a tutorial on P0420 code fix catalyst efficiency below threshold How To Diagnose a p0420 code ...

Jan 26, 2016 | Cars & Trucks

4 Answers

I have 96 buick code p0420.I have replaced the converter and both 02 sensors.mil came back on code p0420. do not know what to do next, help.


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 the exhaust 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.

Aug 02, 2008 | Buick Regal Cars & Trucks

2 Answers

Trouble code po420 2007 solstice


P0420 - Catalyst System Efficiency Below Threshold Bank 1xicon.jpghttp://engine-codes.com/p0420.htmlForum CodePossible causes- Three way catalyst converter Bank 1
- Exhaust tube
- Intake air leaks
- Fuel injectors may be faulty
- Fuel injector leaks
- Spark plugs may be faulty
- Improper ignition timing
- Engine Control Module (ECM) Tech notes The most common cause it the three way catalyst converter Bank 1. Changing just the O2 sensor usually don't repair the problem. If the P0420 code is combined with other codes, try fixing the other codes first.

Jul 06, 2012 | 2007 Pontiac Solstice Convertible

2 Answers

The vsc light and the trac off light and check engine light all came on at the same time code p0420 comes up on my 2005 highlander what does this mean?


A p0420 sets after Engine and catalyst are warmed up, vehicle driven within set vehicle engine speed range and waveforms of heated O2 sensors bank 1 sensor 1 and bank 1 sensor 2 have the same amplitude.
Catalytic convertor and O2 sensors need to be tested

Apr 24, 2011 | 2005 Toyota Highlander

3 Answers

Code p0420


Repair information for the OBD-II trouble code P0420 - Catalyst System Efficiency Below Threshold (Bank 1) Probably needs a catalytic converter

Apr 06, 2010 | 1999 Ford Contour

1 Answer

I've got a CEL P0420 code on a 96 Civic. I've used a scanner tool, and it appears to be a Catalyst issue based on the O2 sensor readings. Both follow about the same frequency. However, I am seeing a Closed...


This code can mean any of the following and not a necessarily bad catalytic converter

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
Check the following
  • 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

Nov 13, 2009 | 1997 Ford Taurus

1 Answer

Error coce P0420 on OB-2 scanner


P0420 = Catalyst System Efficiency Below ThresholdCatalyst System Efficiency Below Threshold. This means that the secondary O2 sensor detects that the catalytic converter isn't working as efficiently as it should. This engine code can be triggered by any one of the following:

1.) The catalyst in the catalytic converter is cracked, clogged, or otherwise damaged.
2.) The secondary O2 sensor is malfunctioning.
3.) There is an exhaust leak.
4.) The computer unit is faulty

Sep 28, 2009 | 2006 Chevrolet Malibu

1 Answer

P0420 code


This means that the secondary O2 sensor detects that the catalytic converter isn't working as efficiently as it should.
This engine code can be triggered by any one of the following:

1.) The catalyst in the catalytic converter is cracked, clogged, or otherwise damaged.
2.) The secondary O2 sensor is malfunctioning.
3.) There is an exhaust leak.
4.) The computer unit is faulty.

Aug 24, 2009 | 2002 Toyota Camry

1 Answer

2000 camry LE 4cyl...p0420


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

Apr 26, 2009 | 2000 Toyota Camry

1 Answer

Diagnostic codes


p1133 O2 sensor insufficent switching (pre converter, left bank)

p1153 ) 02 sensor insufficient switching preconverter right bank

P0420) catalyst system efficiency below threshold left bank

P0151) 02 sensor circuit high voltage pre converter right bank

and p1460 unfortunately I don't have handy..... But REALLY sounds like you need to replace the Oxygen sensors in front of the catalitic converters... There is dual exhaust coming from the engine to one muffler in that truck, there are a total of 2 converters and 4 O2 sensors (1 in front of converter and 1 behind it on both of the pipes) Front ones are definetely shot!!!! Be prepared to put the rear ones in shortly after!!!!! they are about $80 canadian each at the jobbers and probably more at the dealer!!!!!

Feb 24, 2009 | 1997 Chevrolet Tahoe

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