Rob350 Posted January 11, 2017 Share Posted January 11, 2017 (edited) Iv had this code now for about 2months thinking it was a funky faulty cat or o2 sensor so no damage would be done that's why I left it, im about to try and fix it. P0420 - Catalyst System Efficiency Below Threshold Bank 1 or 2 I can't remember which I did some research and tthe rough idea I got was people that had the same code changed the o2 sensor or cat and that cleared it, I looked further into it and people said most of the time it was the o2 sensor I do have a k1 exhaust on my car, and I'm not too sure if the o2 sensor spacers are fitted, but i bought the car with exhaust already on and the code diddnt show up until about 2months/1500 miles after I bought it When I clear the code it only comes back on when I'm cruising around 2k rpm for longer than 5 mins, say on a duel carriageway or motorway, this is nissans technical notes https://www.autocode...420_nissan.html Iv been researching again today and American forums have been saying things like pre cat engine failure, where little bits from the dud cat somehow make it back up into the engine. Now I'm worried. My car is an 04 DE and has got 90k miles with FSH and doesn't burn any oil really, iv done 4k miles in 4months and only topped it up a quarter liter so far one of the fuel dampers is ticking away Nicely if that might make a difference I don't know, but iv just ordered 1 off Jon today so will be fitting that when I get it Do you have any ideas whether its a dud cat? Or sensor? So I'm only buying one have any of you had this before? Is there a way to check and make sure the o2 sensor or cat is faulty before buying replacements? Thanks for any help or advice you have, I'd rather speak to you all than a mechanic or nissan lol Edited January 11, 2017 by Rob350 Quote Link to comment Share on other sites More sharing options...
Ekona Posted January 11, 2017 Share Posted January 11, 2017 Precat failure is a 1zz issue for celicas and MR2s, which forum were you on?? You just need a new O2 sensor, easy as that. Quote Link to comment Share on other sites More sharing options...
Rob350 Posted January 11, 2017 Author Share Posted January 11, 2017 Thanks for replying mate, Cat sensor, or one before cat? Quote Link to comment Share on other sites More sharing options...
Ekona Posted January 11, 2017 Share Posted January 11, 2017 Post cat Quote Link to comment Share on other sites More sharing options...
andybp Posted January 11, 2017 Share Posted January 11, 2017 if you want to check before you spend your hard earned swap the 2 post cat sensors and see if the fault code changes to the other side Quote Link to comment Share on other sites More sharing options...
Flex Posted January 11, 2017 Share Posted January 11, 2017 Post cat Always with the Cat Sorry, hope you feel better soon D. 1 Quote Link to comment Share on other sites More sharing options...
Ekona Posted January 11, 2017 Share Posted January 11, 2017 Cheers bud, I'm not sure I'll make it through the night at this rate though :( Quote Link to comment Share on other sites More sharing options...
Rob350 Posted January 14, 2017 Author Share Posted January 14, 2017 Post cat By post cat do you mean before the cat? (Between cat and engine) Gunna order one tonight Cheers Quote Link to comment Share on other sites More sharing options...
Ekona Posted January 14, 2017 Share Posted January 14, 2017 Post means after, pre means before, so after the cat Quote Link to comment Share on other sites More sharing options...
Rob350 Posted January 14, 2017 Author Share Posted January 14, 2017 I thought there were 1 between engine and cat, and one in the cat? Quote Link to comment Share on other sites More sharing options...
Ekona Posted January 14, 2017 Share Posted January 14, 2017 It's the other side of the cat, it measures cat efficiency. Quote Link to comment Share on other sites More sharing options...
Rob350 Posted January 14, 2017 Author Share Posted January 14, 2017 Cheers just wanted to make sure before I order 1 Quote Link to comment Share on other sites More sharing options...
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