Hi, I have a 2002 BMW X5 3.0i and my problem is real interesting. I am getting a P0430 (Bank 2) code too, but when I swap the two A/F (upstream pre cat) sensors the problem swaps to the P0420(Bank 1). Obviously I bought a replacement, Bosch 13477 A/F sensor on Amazon and swapped it out with the sensor I figured was operating poorly. The new one in,... and still got the code. Got another one (replacement as I thought they sent me a bad new one) and same problem.

What is seriously odd is that the used sensor that doesn't trigger the code, no matter what Bank I put that one in, no code, ONLY in the other bank with the "new" sensor does the SES light come on. I don't see how it could be anything beyond the sensor... BUT it's NOT the CATs or they would trigger no matter what sensor is in... right?!

Can't be the CAT or it would show up on the same bank.
Two new bad sensors? what are the odds?

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2002 BMW X5 3.0i