# MIL and OBDII code P0421



## sonnybihis (Feb 4, 2009)

First of all I hope I'm in the right forum, sorry if I'm not. Hopefully I can get help anyways. I got a MIL on Saturday. It came up as P0421 Warmup Catalyst low threshold (Bank 1). I erased it and it didn't come back until today...maybe 250-300 miles later...when I took the car in for a smog check. The results of the smog check don't show any emissions out of spec so I'm assuming the problem is with an O2 sensor. Has anyone had any experience with these? Can this O2 sensor be removed/cleaned/replaced, or does it need to be replaced w/ a new one. Please let me know. Thanks!


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## sonnybihis (Feb 4, 2009)

i just found this...
http://www.vaglinks.com/Docs/A...e.pdf
i hope that fixes it!


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## sonnybihis (Feb 4, 2009)

*Re: (sonnybihis)*

i went to the dealer and they want $500 to diagnose the problem and update the ECM. i think it's wrong that they wanna charge me for a known issue with this ECM...


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