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I need to replace the lower o2 sensor on my 96 civic (Lx, Auto), and I was curious whether there was a difference between the first and second (pre and post cat). They look the same to me at first glance, but when ordering online it looks like it usually has it specified whether it's the "upstream" or "downstream" sensor... so I'm worried there's a difference.

Also, does anyone have any suggestions for what to buy and where from?

I was going to do Bosch OE Identical Part/Stock # 13007, but that one reads "Front" under location... and there's a separate one that reads "Rear" (Part#: 13249), and the only difference I can tell is that the front one has wires that are about 4 inches longer.

Thanks.

 
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big difference. the stupid parts store sold me the rear instead of the front and i had major issues with unsteady rpm and lurching forward from a stop. they are not the same at all. i now have bosch oem for both sensors, primary/upstream and secondary/downstream (in the cat).

 
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Sorry for the thread revival but I didn't want to create a new one:

So was OP right?

Are those the correct P/N?

 
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do you have 7thgen or 6thgen? there are two completely different sensors for upstream/primary and downstream/secondary.

 
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I have a question. While driving and holding a constant pressure on the trottle pedal, engine rev fluctuates. What can be the problem?

 
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I have a 6th gen.

 
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98 Civic DX Engine light is on.,diagnostic says I need front oxygen sensor.How tricky is that to install? My mechanic friend says it's not real important to get it fixed soon, but wont it improve my mileage?