Hi I havea problem on 2002 taurus ses 24 v duratec just bought and am sure problem existed before. current problem is zero voltage coming from both oxygen sensors. bank 1 sensor 2 was throwing code p136 so replaced it and still had code. i bought a obd2 data reader and saw b1s2 sensor gave no voltage or small[.05] so i switched both sensors b2s2 ,b1s2 and got readings on both for about 2 mins. then b1s2 slowly went to zero . switched them back and now dont get voltage from either. no codes thrown. b2s2 did give normal voltage before switch. past problems, codes for misfire cyl. 6, misfire first 1000 revs but have gone away. changed coil , fuel filter , b1s1 and b1s2 oxygen sensor.
also changed pcv
Low voltage means a lean condition is possible. Either too little gasoline or too much O2 in the mixture. Is the engine showing signs of overheating at all? Any drivability problems, like engine stuttering or lack of power?
Since the code seems to be for sensor 2, that’s probably the post-cat sensor. So one idea, your cat could be bad. Another, if this is a heated sensor, there’s something wrong with the heater circuit. Usually that would throw a code though.