We're getting "check engine" messages more frequently now that read "O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)." I assume this means (a) time to replace the sensor, and (b) it's the before-catalyst sensor. Yes?

Some questions:

1. There's a $65 difference between the OEM from eEuroparts and the generic Bosch sensor from "alloemvolvoparts.com". I've used generic sensors for a while on my 1987 740 and 1982 240, and they've been fine. I will admit the four-wire sensor's looking a bit more intimidating, though. How easy is it wiring a generic one?

2. The eEuroparts listing says, "Must also use updated harnesses 9202714 (x1), and 9202715 (x1)."

3. When I look down from the top, there's a sensor visible sticking out of the exhaust pipe right down there the pipe disappears under the body. Is this the front one?

The front one is the one that usually goes out. It's before the cat. sticking out of the lower part of the exhaust manifold. You can get the one without the correct adapter for cheaper but will have to splice the wires. I understand that the wires are all color coded and difficult to screw up.
--
1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon. My cars have been running so well lately they've got me worried.