1997 Chevy Cavalier catalyst converter

1997 CHEVROLET CAVALIER
195,000 MILES • 4 CYL • FWD • AUTOMATIC
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DAVIDFARR3000
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hello, i am having a problem with my car which involves the code P0420, catalyst efficency below bank 1, what is the cause of this? i replaced the oxygen sensor that goes into the manifold, is there another one at which i need to replace? or is the problem with the catalytic converter itself? if that is the issue can i remove it and replace it with a pipe? i live in minnesota and am pretty sure that that is legal, i would appreciate any advice, thanks
Sep 27, 2009 at 11:34 PM
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MMPRINCE4000
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The code indicates the downstream (after convertor)O2 sensor is getting abnormal readings, out of range.

Most likely the sensor is bad, but could be the convertor. A backpressure test will tell you if the convertor is bad.

It is illegal to remove the convertor, this is a Federal law, not a state law.
Sep 28, 2009 at 7:36 AM
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DAVIDFARR3000
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where can i get a backpressure test done and what would it cost? i live in minnesota
Sep 28, 2009 at 11:12 AM
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MMPRINCE4000
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Call around and ask repair shops for a quote. Some muffler shops can perform this.

They will probably charge 1 hour shop time, usually $85-100.

If convertor is bolted to exhaust, you can remove it, look inside. Should be a honeycomb, grayish color.
If you see any melting/cracking or sooty material, convertor is most likely bad.
Sep 29, 2009 at 9:18 AM