Thanks Kevin,

How valid do you think testing the catalyst is by looking at the pre- and post-cat O2-sensors?

Something like in these images:

[1999 Audi A4, HO2S Waveform] as a bad cat, and this;

[1999 Audi A4, HO2S Waveform] as a good cat.

I realize ... Login to read more.

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