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156 Posts
Totally agree. I have a worn cat at 200K mi. due to previous engine issues. To further clarify, from my own experience with p0420, the "catalyst efficiency" can be made to increase and exceed the threshold by which the p0420 code is set by correcting the engine issues. When monitoring my engine using Torque Pro ($5.00) and an OBD2 bluetooth adaptor ($35.00), I can track the pid "catalyst efficiency" in the "test results" tab. When my engine performance or driving habits contribute to a normal above threshold cat, the listed efficiency range is .35 to 4. My cat is usually .465 to .6, or above the .35 threshold, ie no p0420 code.
When the 420 code and cel is set, the listed efficiency range changes to .5 - 4 and my cat's efficiency has typically dropped to .3, or below the original .35 threshold. My guess for the increased threshold is to force a repair so that the numbers don't bounce back and forth without a resolution to the problem.
The code pops on from my engine's performance during excessive idling, sitting in traffic for hours, and once when I taught my daughter how to park for hours in slow motion
The code happens a couple times a year.Although my cat's .3 will increase to .465 just by resuming normal around town or highway speed driving over the course of several drive cycles, it will not exceed the .5 threshold necessary to keep the cel off. So I erase the code and wait for several drive cycles to once again have a "ready" catalyst on my emissions ready tab because the range returns to .35 - 4. And my cat number gradually increases to .6 until the next occurrence.
It is a game until I successfully repair the engine issue. The car runs great and the numbers look normal except under those seldom "extreme" conditions.
Too many words but my point is also, don't buy a new catalytic converter to turn off the p0420 cel without fixing your engine or discovering the cause first. New year's resolution, I gotta getta a smoke machine...
imho
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