98 explorer check engine light lit wOBD codes 171 174 that say the airfuel ratio is too far out of spec for the control module to correct it. Could this simply be an O2 sensor gone bad or what?

Yes and no. I have a 99 explorer xlt, I found my thermostat stuck open which would not allow engine to come to operating temp. The o2 sensors only work properly if engine is at operating temp.It also could be the ECT sensor(engine coolant temp).I suggest changing thermostat first then clear code and drive 50-60 miles then retest.