I own a 1999 S70, I have a problem with my O2 sensors. I was thinking of changing them myself ( is this a easy job ) and where are they located.
And where can I get the sensors...

A straight forward job unless the sensor is seized in its hole. I think the S70 is like the 850. There should be two, one in the exhaust pipe just before the cat converter and one in the pipe just behind the CC. Hopefully one of these guys will correct me if I'm wrong. They resemble large spark plugs with four wires. Get Bosch sensors ( not aftermarket generic ones) and make certain they are correct for your engine. You can get two types, a "direct fit" and a "universal" with the latter being cheaper but will require you to cut and splice the wires with a splice kit which is straight forward. See Bay 13 for pics and step by step instructions of the procedure.

bl

Out of curiousity, what are the symptoms of a bad O2 sensor?

Hi MFahsel,
I really don't know what the symptons are of the sensor my mechanic did not give me that information. I also know there is a problem because the check engine light is on. The car has 59,000 miles on it and I just got a 60,000 mile service last week. Thank you, Steve

do you have a quote for them to change out both O2 sensors from this guy?

Does anyone know if the ECM specifies which O2 sensor is bad when the CEL is lit? I'm trying to understand why they seem to do both sensors. Is it that they're money-grubbing or just necessary? After all, they seem to die anywhere from 55,000 mi. to >130,000....