Oxygen Sensor Testing?

[OOMPH!]

If your check engine light is not on can you assume your oxygen sensor is operating properly?

I say yes, also if your exhaust has a weird smell (carbon dioxide) then your O2 is probably bad.

You cant smell carbon dioxide. You can however smell hydrocarbons. :P ;)

pffft......you get the idea

[Speed25]

You can use any Bosch four-wire O2 sensor (even Bosch's website says they're all the same). Find one for about $40 at any parts store, then splice on the connector. I found a write-up on it somewhere (no clue where), and tried it. Saved $40 and it has worked perfectly.

[GreekDriver]

I'm not a competent fella... I might need some more help with this. I searched the web, but the cheapest O2 sensor from Bosch I could find was 75 dollars. Could one of you guys point me in the direction of a cheaper one? I was searching for 3 wire sensors and 4 wire sensors. Also, I searched the boards and Googled the web for the instructions on splicing. I found this:

the BMW is 4 wire, the 4th wire is gray, and all it is, is a ground...splice the other three wires to there respective colors (black and white) and ground the other one....cut the stock sensor cable near the o2 sensor then the ford sensor near its connector. not hard, i did it in under 20 minutes

That doesn't completely make sense to me. So the wires are color coated, the new sensor has 3 wires. I put the black and white together, what about the other 2 wires? I have one Ford sensor wire left, what do I do with the third and fourth BMW wires?

This is greatly appreciated, I'm really glad I don't have to shell out that much cash on such a small part. Thanks guys!

[GreekDriver]

Some more searching yeilded the Bosch 13275 Sensor which is a 4 wire sensor. It's about 40 bucks. Are the wires colour coated for a direct splice? Thanks!