Hi, I know this is on old thread but thought to ask. I was just working on replacing the oxygen sensor on my honda Civic 2001 EX and noticed after I took the upper sensor out that the tip of the sensor was way smaller than the new one! Does that matter? I purchased Bosch aftermarket and not sure what brand the old one is. It was rusted and black!

I thought to check about this first before I try to put the new one in. The new part is an exact fit to my honda according to Bosch.

Thanks

 

Different brands will look different. That said Bosch O2 sensors don't work well in Hondas. Denso or NTK are a much better choice.

 

Thanks for the info. I did install the new Bosch sensor and now my car is throwing P0420 code (catalyst system efficiency below threshold) for the first time! Is that why Bosch sensors don't work well on Hondas? Or am I looking at a new problem?

Thanks again.

 

No, usually you'll just start throwing an O2 sensor code again prematurely or it will just keep throwing an O2 sensor code.

The code you have is generally caused by an exhaust leak ahead of or at the catalytic converter (often it's due to a hairline crack in the manifold where the primary O2 sensor screws in) or the catalytic converter itself is bad. Either way the catalytic converter generally needs to be replaced (if it's cracked you can try welding it, but it rarely works.

 

I pulled my original O2 in my exhaust mani the other day. I was expecting a fight so i got the engine "warm" spayed it down with PB Blaster and waited a while. Came back respray let soak again. After that it came right out with just an open ended wrench.

Denso or NGK FTW

 

The catalytic converter was replaced three years ago. I had both O2 sensors fail recently with codes P0135 and P0141. I replaced only the upper stream sensor today with the aftermarket Bosch just to make sure it works fine before putting in the second sensor and realize later that I should have gotten ngk or denso instead. What is strange is the lower stream sensor is not throwing a code anymore and I was surprised to see the catalyst low efficiency code appear for the first time on the scanner! I drove the car for less than 5 miles and I might drive it more just to see if anything changes. Shall I just replace the second sensor anyway or it doesn't matter at this point?

Thanks a lot for your feedback