# catalyst system



## cricketg4 (Jan 26, 2010)

riding down the road the other day. CEL came on. cant remember the code but it said catalyst system below threshhold bank 1. does that basically mean i need a new cat?


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## cricketg4 (Jan 26, 2010)

anybody? any help appreciated


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## zanegrey (Dec 5, 2005)

the only way to check the cat is to remove it and look thru it..


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## cricketg4 (Jan 26, 2010)

but what does that code mean


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## zanegrey (Dec 5, 2005)

post the code...


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## cricketg4 (Jan 26, 2010)

i cant remember the actual code. i just know that it said catalyst system below threshhold bank 1.


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## zanegrey (Dec 5, 2005)

that codes appears to be for a v6 engine..

a v6 engines heads are designated bank 1 and bank 2..

i suggest you clear the codes and re read them...


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## cricketg4 (Jan 26, 2010)

ok thanks will do


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## smj999smj (Jan 1, 2006)

SHould be a P0420 code and you do not test it by looking though the converter. You need to have a scantool to monitor the front and rear oxygen sensor signal cycles while driving. If the catalytic converter is doing its job, you will see approximatly two signal cycles (rich to lean) from the front sensor compared to each signal cycle from the rear sensor. A 1:1 ratio means the catalyst is inefficient and the catalytic converter needs to be replaced. Testing includes checking the O2 sensors for proper operation and checking for any exhaust leaks, among several other steps. But most of the time if the exhaust is in good shape and the engine is running well, chances are a P0420 code will mean the cataylst is bad.


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## lilfoo22 (Mar 22, 2010)

[email protected] through it. and +1 for smj!


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## smj999smj (Jan 1, 2006)

Well, looking through the converter would be okay if the converter was clogged, but there would be more issues than just a CEL. Plus, I would prefer to use an exhaust backpressure tester to test for a clogged or restricted converter. P0420/430 codes are usually caused by the media inside the converter becoming inefficient at converting the exhaust gases. It won't cause a performance problem, but it will cause a CEL issue on a vehicle with a rear O2 sensor, which is solely there to monitor the efficiency of the catalytic converter.


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## lilfoo22 (Mar 22, 2010)

i concur................


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## saudade (Apr 10, 2010)

You can also see if the honeycomb is intact. Loss of sufficient surface area will also degrade efficiency. You'd also likely hear a rattling sound while banging on the CAT from the debris. Holes in the casing can also affect sensor readings (as any leak upstream can).

So a visual inspection is a valid step in troubleshooting. It's basically free, requires no special test equipment and minimal effort.


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