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Po420 code what or where doi start to diagnose this problem

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This is catalytic con.problem but could be vacuum leak,exhaust leak or could be nightmare.

Posted on May 06, 2013


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P0420 p0522 chrysler pacifica CODES

thje po420 need to monitor o2 sensors to verify if you have a bad sensor or bad catalitic converter
the po522 oil presure sending unit

Oct 15, 2014 | 2005 Chrysler Pacifica

1 Answer

If you reset PO420 code can you still diagnose problem

When it returns. P0420 is a bad catalytic convertor. Nothing else will set this code. It will need to be replaced.

Aug 09, 2014 | 2005 Acura MDX

1 Answer

Fault coade

You will get a 420 if the Exhaust Converter is worn out.

You need professional tools to diagnose that

Mar 11, 2014 | Volkswagen Jetta Cars & Trucks

1 Answer

Po420 code on an 2001 dodge neon

The code means the catalytic converter is not functioning as it should, sometimes because the engine is not reaching operating temp, and sometimes because of a fuel problem.
You may need to hook it up to a scanner and watch the sensor readings to diagnose the problem.

Sep 20, 2012 | 2001 Dodge Neon

1 Answer

Catalyst operating below threshold 01' S80 what do I check for/ how do I fix this problem?

The Exhaust Converters are worn out
PO420 & PO430

Replace them & then diagnose any other
code issues, from there.

Jun 04, 2012 | 2001 Volvo S80

1 Answer

My 2000 Cadillac Deville engine light on. Engine code PO420

Catalyst System Efficiency Below Threshold (Bank 1)

A code PO420 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 reading

  • 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

May 11, 2011 | 2000 Cadillac DeVille

1 Answer

Hi my 2001 buick lesabre has a diagnosic code of po420.....My car will die while Im driving . Can u tell me what this is??

P0420 indicates a problem with catalyst efficiency on bank 1 of the engine. It is likely that the catalytic converter is faulty.

Aug 12, 2010 | Buick LeSabre Cars & Trucks

1 Answer

What is this code po420 bank 1 in a che?vy monte

I could go on and on about Po420 code but it's easyer to tell you to go to and everything you want to know and then some is there. Let me know if this was helpfull..4 thumbs up !

Feb 24, 2010 | 2002 Chevrolet Monte Carlo

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