I've gotten a P0422 off and on (it has cleared itself a couple of times). It's gone a week between setting off the MIL. I searched the archives here, and it seems the recommendations have been to replace O2 sensors (typically front?) and also possibly the catalytic converter. With this turning itself on and off, I'm thinking that one of these items must be on the verge of failure. I have an OBD II scanner, which has all the codes listed in the back, but does anyone know of a definitive reference that gives you more information besides just the few words on each OBD code? Is there a book or CD that elaborates on where what these codes translate into looking for failed items on your car? Some codes are fairly descriptive, but others are pretty vague (like the P0422).

Any ideas as to the on and off P0422 or a better reference for giving more info on OBD II codes? Thanks in advance.
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Don 01 V70 2.4T 96 850S