IN 2007, THE CK ENGINE LT CAME ON, AND A DIAGNOSTIC TEST INDICATED THAT OXYGEN SENSORS HAD TO BE CHANGED. THE UPSTREAM AND DOWNSTREAM SENSORS WERE REPLACED. IN 2008 THE CK ENG LIGHT CAME BACK ON SAME RESULTS, AND BOTH SENSORS WERE REPLACED. THIS YEAR THE CHECK ENG. LIGHT CAME BACK ON. THIS TIME THE SAME TBLE CODES P0171/P0174 WERE DISPLAYED. THE CAR HAS NO PERFORMANCE PROBLEMS, HOWEVER THE VEHICLE CAN NOT PASS A NY STATE INSP. WHAT CAN BE DONE TO CORRECT THIS CHECK ENGINE PROBLEM FROM RECURRING?
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2000 Ford Windstar Question: CHECK ENGINE LIGHT ON CONSTANTLY
Answer #1patrick mannion from Greg Solow's Engine Room, July 26, 2009, 22:59Master
I have seen repeat O2 sensor failure on the 3.8 Ford engine due to a mildly blown head gasket. Coolant contamination destroys the sensor. On removal of the sensor you will notice green deposits on the O2 sensor tip!
Sensor performance should be able to be monitored using a higher quality scan tool monitor live sensor pattern and voltage determining if the sensors are the actual problem or not.