p0422 Main catalyst below threshold error - VW Forum :: Volkswagen Forum
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post #1 of 3 (permalink) Old 07-08-2009, 07:18 AM Thread Starter
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p0422 Main catalyst below threshold error

I have a 1998 VW Jetta GLX VR6 and am having trouble clearing the p0422 01 error.

The first thing i tried was i replaced the catalytic converter, front o2 sensor and rear o2 sensor. I then cleared the error and drove on the car for about 25 - 30 mile and the error returned. I just put a spark plug non-fouler spacer in hoping that it will help clear the error (maybe it related to a different cat? The new cat is nothing special so i figured it wouldnt be a problem). I also tried clearing the computer by unhooking the battery for a couple hours.

I have two questions really. The first one is whether i should drill out the hole on the non-fouler to 1/2''. I drilled it out but left the 1/4'' hole at the end because i wasnt sure. Should i have drilled it 1/2'' all the way through?

Second question, is there anything else i can do to diagnose the problem? what sort of other components could be throwing the p0422 error?

Any help on this would be helpful i have done all that i can think of to clear the error but to no avail.

Thank you.

EDIT: I put the non-fouler on the rear o2 sensor. There are two o2 sensors in this setup, one pre cat and one post cat.

Last edited by sumone4life; 07-08-2009 at 07:30 AM.
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post #2 of 3 (permalink) Old 07-17-2009, 01:53 PM
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I had that code too and I changed both upstream and downstream o2 sensors. But I noticed that the signals were very erratic. I bought some MAF sensor cleaner and cleaned the MAF and everything seemed to work alot better. Might not help you out, but can't hurt to try.
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post #3 of 3 (permalink) Old 05-08-2010, 11:21 AM
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your signals were probably erratic due to poor metering up front , not to mention a bad metereing job is made worse by extra non metered air.


as for the OP issue , i would say to see if you can get a tech2 hooked up , for cheap , and see your o2 crosscounts. if its rediculously high , i would say clean your maf , if it looks normal , you may have contaminated the o2 sensor.

can i get a pic of this spark plug setup? i think its what im looking for on mine..

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