1999 Chevy Astro code PO420 meaning

Tiny
SHYANNROSE
  • MEMBER
  • 1999 CHEVROLET ASTRO
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 160,000 MILES
Took car to autozone and got this code, definition is catalyst efficiency low bank 1. What does it mean and how can I fix it to pass emmissions? Or how I bypass it to pass emmissions? Car runs fine but code still appears. If I clear the code will it pass emissions?
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Wednesday, August 19th, 2009 AT 6:18 PM

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Tiny
RASMATAZ
  • MEMBER
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

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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Wednesday, August 19th, 2009 AT 7:53 PM

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