Hi, and welcome to Just Answer!
The code indicates that the oxygen sensor is sending a rich (or to be more technically correct a low oxygen) signal to the engine controller that it's unable to compensate for by adjusting fuel delivery.
Any problem that causes the car to be rich can trip this code.
- failed oxygen sensor - if the sensor fails and sends back a bad reading to the controller (in this case something greater than .5 volts) then this code will set. One of the more common reasons.
- high fuel pressure - if the fuel pressure is excessively high it will skew the system towards rich, the computer detects this and you'll get the code
- purge solenoid - if the purge solenoid fails, it can allow excess fuel vapors to be drawn in when the computer isn't requesting it.. possible but unlikely to occur without some other codes relating to the purge or evaporative emissions system
- bad map sensor - if the sensor is out of calibration it'll throw the fuel delivery calculations off.. unlikely without other DTC's but possible
- throttle position sensor - pretty much the same story as the map sensor.
Without access to a scan tool to display live data and verify sensor readings, the best place to start in my opinion would be the oxygen sensor itself. They are really a tune-up part in my opinion and should be replaced on a regular basis anyway, just to maintain engine performance and economy. I do not however care for the 'universal' wire it yourself type that many parts stores sell, often times they cause more trouble than they are worth..
The sensor in question is of course the one that's more harder to get to, it's the one located in the exhaust manifold, just before the flange for the catalytic converter.
I hope this helps, if you need more information, or have more questions, please don't hesitate to reply back and ask!