Hey I had the same problem. Bought my Jeep and the idiot light (Maint Required) Light was on. Drove the wife nuts. After researching this subject, courtesy this forum, I determined nothing was wrong. Its a automatic light. Comes on at a predetermined mileage. Older Jeeps (pre 91) had a mechanical sensor located near the accelerator pedal. Jeeps strating at 91 had it built into the computer. If your Jeep is running ok and passes emissions dont waste your money, forget about replacing the O2 sensor. Just unscrew the 2 screws that hold the cover for the warnig light panel and remove the Bulb. Trust me it works. If the o2 sensor is going bad you will know it. You will lose power at highway speeds and the engine will run like crap.
"If It Aint Broke, Fix It Till It Is!!!!!"
05 TJ Rubicon, 4.0L, 6 Speed.
07 Ram 1500 Quad Cab