This is the OBDII error that I got on my 1999 Windstar. I've seen the "Possible Causes" list: blown fuse, short to VPWR in harness or HO2S, water in connector (not likely the last week or so), open VPWR or GND circuit, low battery voltage, poor electrical connections, HO2S heater, and PCM. Is it likely that replacing the Heated Oxygen Sensor will fix the problem?