P0420 Code
07-27-2016, 10:40 AM
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My Ride: 2005 525i
P0420 Code
So my check engine light came on last night and when I checked what it was this morning I got the P0420 fault code. I read other posts here and other forum online that the most common issue are bad oxygen sensors. But before I spend $400+ on 4 new sensors I wanted to be sure there could be nothing else that could be causing that. I've heard it is very difficult for the cats to go bad so that's my last resort. Thoughts?
07-28-2016, 07:05 AM
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I have also found that adding a fuel cleaner (Techron or Lucas) for several fuel tanks can clear this signal. Its worth a try.
07-28-2016, 02:57 PM
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The fault read Bank 1, what exactly is Bank 1, is that the pre-cat sensor?
I've read that as well, but should I put cleaners in each time I fill up on fuel?
What're the possibilities that the cats are bad? Car has 120k, however the engine was recently replaced with another one that had 62k. Cats were not replaced, I just used the same. Ones. Car runs smoothly though. The replacement engine came with its own O2 sensors which I used when I put it in. I still have the old ones, but they have white residue on them, not sure if that's a bad thing?
I've read that as well, but should I put cleaners in each time I fill up on fuel?
What're the possibilities that the cats are bad? Car has 120k, however the engine was recently replaced with another one that had 62k. Cats were not replaced, I just used the same. Ones. Car runs smoothly though. The replacement engine came with its own O2 sensors which I used when I put it in. I still have the old ones, but they have white residue on them, not sure if that's a bad thing?
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