Agiyo

The downstream O2 sensor on my '05 S2K has been problematic for some time, as discussed in a previous thread about Costco gas vs. Chevron. The real problem apparently happened about the same time I filled up with the Costco premium, then shortly afterward, I got a check engine light, code P0420. Turned out, something had nicked the wires just outside the sensor. The best patch and reinsulation I could put on it lasted through the winter, then another CEL.

I read forum discussions about O2 sensors. Based on the testimonies that sounded like someone knew what he was talking about, I ordered Bosch sensors. Long/short, it didn't work. Threw a P0161 code, though I rechecked everything and believe I'd gotten my part right. When I revisited the forums, folks said Bosch sensors were hit and miss in S2000s, so I looked for an OEM Denso. Dealer wanted $341 to have it here in a week, $361 to have it here tomorrow.

Discount Import Parts, down across from Washington Square, got me the same Denso part, albeit without the HONDA tag on it, in 4 hours, for $52. Works like an S2000 now. Hooyah.

Your mileage will undoubtedly vary.

cdelena

Yes, I have had good luck with cheap ebay sensors.

Sabre

I don't remember the brand I got from rock auto when my cat failed on the ap1. But whatever it was worked great. It might have been a denso. But it was about the same price, 60ish.