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I got a new catalytic converter for my Honda Civic 2005 HX car because the "coal" inside went lose and was just making noise inside of it. While trying to take off the old O2 sensor I ended up rounding it and in frustration I cut its wires and now it is no longer functional.

A friend told me he has an old O2 sensor for his Civic, but it went on the catalytic converter that was on the header not on the secondary catalytic converter.

So let me give you the idea, my HX Civic has 2 catalytic converters and 3 O2 sensors. An upstream one before both of the catalytic converters and 1 after each catalytic. My question is can I interchange the O2 sensors after the catalytic converter?

  • I don't know for sure do I'm not going to answer, what I would say is that those sensors are important for your engine to run efficiently. Used, old ones may not be accurate and could reduce gas mileage, costing you money. It's a false economy. – GdD Sep 27 '18 at 9:04
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Your HX has a D17A6 VTEC engine in it. Looking for O2 sensors for the vehicle, I'm seeing both the center and last O2 sensors should be interchangeable (RockAuto.com shows the ACDELCO 2132890 will fit in either position). The lead O2 is definitely not. As long as your friend's car is a 2001-2005 Civic HX, it should work, but the O2 is specific to these years. As far as I can tell, it's not used for any other cars nor any other years beyond those mentioned.

I agree with what GdD is suggesting, though. If this is a stopgap measure to get your car up and running, I get it. I personally would be replacing it soon, though, because the old one is ... well ... old. Get it replaced with a known good one as soon as possible.

  • The o2 sensor on my friends civic was on an LX not an HX would they still be interchangeable? Also I thought since this was just telling the ECU the condition of the catalytic converters and it had nothing to do with the fuel trim so it should not affect the performance at all? The CEL was already one due to my faulty cat before replacement. I just spent A LOT of money to get the new cat and If I could save a few bucks on the o2 I would be a lot more content – method Sep 27 '18 at 14:33
  • @method - you could try, but they are not the same. The LX isn't even a VTEC engine. They are showing two distinctly different part numbers for the sensor. I don't know what the difference is between the two. I mean, it could just be wire length, but who knows. All I can say is: you can try. – Pᴀᴜʟsᴛᴇʀ2 Sep 27 '18 at 15:06
  • The downstream O2 sensors tells the ECU if the output of the catalytic converter(s) is expected based on the adjustments to fuel trim based on the upstream O2 sensor. They have different ranges they measure. I suspect they cannot be interchanged. Additionally, there is no "coal" in a catalytic converter. There is a metal frame structure with semi-precious metals that, when heated, convert gasses flowing through to less toxic gasses (such as CO to CO2). And, yes they fail and are expensive. – Dacid Salin Sep 28 '18 at 4:52

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