P0420: Dreaded inefficient catalyst

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hootz
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P0420: Dreaded inefficient catalyst

Post by hootz »

I recently did battle with a P0420 code. The PCM samples the pre catalyst oxygen sensors and compares those readings to the post catalyst oxygen sensor to determine if the catalytic converter is doing its job properly. I could not get a hard explanation on what exactly the PCM looks for when comparing the pre and post oxygen sensor readings and the exact parameters for setting the code. I watched my post sensor with a graphing scanner while driving in all types of conditions. It was usually a steady line with a few slants up or down, when slowing to a stop after highway operation it would cross from rich to lean a few times (cross counts). After my experiment I think the PCM looks for a steady reading from the post oxygen sensor. There is probably some kind of threshold as to the number of times for the post sensor to cross from rich to lean.
One thing that really helped to diagnose this trouble was to use an oxygen sensor simulator such as this one: http://www.bigdaddiesgarage.com/straight-cel-fix.html

This device moves the sensor further away from the exhaust stream and makes it less sensitive. A real handy device to tell whether the converter is actually inefficient or the problem is elsewhere. So far my test has shown that the converter is just on the ragged edge of being inefficient and the code has not reset with the simulator installed. :idea:
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Re: P0420: Dreaded inefficient catalyst

Post by F9K9 »

That "simulator" can also be found at your local parts store HELP section but, is known as a "spark plug non-fouler"

Image

Part # 42002 would probably work for the S-10. It's used in a lot of different rigs to get rid of a MIL. I have a couple that I need to install on the 2 mini cats in my heep until I can afford a replacement from Rock Auto.
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Re: P0420: Dreaded inefficient catalyst

Post by hootz »

The non foulers will work and save about 10 dollars. There is a little extra labor involved to drill out one of the non foulers for the sensor tip to clear.
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Re: P0420: Dreaded inefficient catalyst

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hootz wrote:The non foulers will work and save about 10 dollars. There is a little extra labor involved to drill out one of the non foulers for the sensor tip to clear.
That's right and I meant to mention that but, forgot. I don't recall the drill bit size but, I had one and with a vise it took under a minute. A yr ago before the garage, vise and workbench it would have been an ordeal using a visegrip, standing on it and trying to drill it out. :roflmao:
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Re: P0420: Dreaded inefficient catalyst

Post by roadrunner »

Given your duck problems Reed you most likely would've drilled your foot with the vice grip/drill combo.
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Re: P0420: Dreaded inefficient catalyst

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roadrunner wrote:Given your duck problems Reed...................
Shhhhhhhh, dammit. They haven't figured out that I am still wrenching, just outa sight. :roflmao:
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Re: P0420: Dreaded inefficient catalyst

Post by roadrunner »

Ooops I forgot you have a reverse duck blinder (garage). Don't eat any beans they might think it's a call to come feed. hee hee hee
2001 CC LS, pewter, stock, 4.3,Wait4meperformance, CFM throttle blade, Helix throttle body spacer, 4spd auto, 3button electric 4x4 shift, heavy duty factory suspension, Bilsteins, 1" rear wheel spacers, skid plates.