'04 Oxygen sensors

I wanted to do a little bit of preventable maintenance on my car by replacing the oxygen sensors. The car is supposed to have two sensors. The one up front I found but I can't see any others. Where should I look for it? Also is there anything I should watch out for with the replacements sensors? Is one brand better than another?

Your 2004 will have at least 3 O2 sensors, and probably 4 sensors. There will be one for each cylinder bank between the exhaust manifold and the catalytic converter and one after each catalytic converter. I believe your car will have a separate converter for each cylinder bank and therefore there's likely to be a sensor after each of the converters. The pre-cat sensors are "Bank 1/2, sensor 1" and the post converter sensors are "bank 1/2 sensor 2."

I'd suggest you get sensors specific to your application (ie: not the universal fit type that you will need to solder your existing connector on to). I've used the Bosch sensors without issue.

-Rod

That's very honorable of you, but I wouldn't spend the $$$$ unless indicated to do so. My 87 Taurus had one o2 sensor, the factory original, lasted 170k+ until I junked the car due to frame rustout, mechanicals were excellent, original motor, clutch, trans, factory a\c converted to 134a still worked, orig compressor. Only code related to o2 I ever got was a lean code, which I traced to a corroded dedicated ground wire bolted to the engine block, orange in color. At that time, maybe now too, Ford was using a dedicated ground wire on that circuit, no splice. In fact, got that idea to check from a Ford mechanic who pretty much guaranteed if I cleaned up the connection presto chango it would test out clean , not to say maybe it wasn't switching a little slower there at the end with all the miles. I had tested it with a propane torch and a sensor tester at one time, passed that.. of course that's just a light on-off test, in milliseconds who knows, plus you've got obdII, whole lot more picky then obdI.. I don't believe in changing them as part of some routine maintenance schedule, too expensive.. best thing change the oil every 3k, 2k if you're keeping it to the bitter end. Boy did I get off-topic here. I can't stand to see people spend needlessly.