Ford Windstar 1999-2003

Heated Oxygen Sensor



The heated oxygen sensor supplies the PCM with a signal which indicates a rich or lean condition during engine operation. The input information assists the computer in determining the proper air/fuel ratio. A low voltage signal from the sensor indicates too much oxygen in the exhaust (lean condition) and a high voltage signal indicates too little oxygen in the exhaust (rich condition).

The sensors are threaded into the dual converter Y-pipe. Heated oxygen sensors are used on all models to allow the engine to reach the closed loop state faster.

Heated oxygen sensors are located in the dual converter Y-pipe both before and after the catalyst.


  1. Disconnect the HO2S.
  3. Measure the resistance between PWR and GND terminals of the sensor. Resistance should be approximately 6 ohms at 68°F (20°C). If resistance is not within specification, the sensor's heater element is faulty.
  5. With the HO2S connected and engine running, measure the voltage with a Digital Volt-Ohmmeter (DVOM) between terminals HO2S and SIG RTN (GND) of the oxygen sensor connector. Voltage should fluctuate between 0.01-1.1 volts. If voltage fluctuation is slow or voltage is not within specification, the sensor may be faulty.