Inactive O2 Sensor

Ok i own a 97 GC, its been spitting and sputtering lately, and the SES light has been on for quite a while, my dad used it to get to work and back and it has been rather neglected, the engine is coated in oil (Possibly Oil Pressure Sender Unit???), and sparks are probably bad due to this... Anyway its the 3.0 by the way and when we threw it on the datalogger it spit out the "inactive 02 sensor" code... So i was wondering if the 02 sensor is bad or if it just needs some work on the wiring? It may not even be that at all, could be sparks or vaccuum lines... Please help...