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Old 05-05-2002, 05:30 PM
Arthur Dalton Arthur Dalton is offline
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,768
Seeing that you have the sensor out, you may want to try this. It is not as good as testing the system in the car, but will tell you if your sensor is generating a signal and cycling...
I can't see if you have a 3 or 4 wire sens in your pic,,, but if it is 4 the ground is the gray wire . If 3 , the case is ground [- neg..]
The 2 white are heater and you may want to see if you have continuity there while you are at it.

<<For testing the sensor out of the car, use a high impedence DC voltmeter as above. Clamp the sensor in a vice, or use a plier or vice-grip to hold it. Clamp your negative voltmeter lead to the case, and the positive to the output wire. Use a propane torch set to high and the inner blue flame tip to heat the fluted or perforated area of the sensor. You should see a DC voltage of at least 0.6 within 20 seconds. If not, most likely cause is open circuit internally or lead fouling. If OK so far, remove from flame. You should see a drop to under 0.1 volt within 4 seconds. If not likely silicone fouled. If still OK, heat for two full minutes and watch for drops in voltage. Sometimes, the internal connections will open up under heat. This is the same a loose wire and is a failure. If the sensor is OK at this point, and will switch from high to low quickly as you move the flame, the sensor is good. Bear in mind that good or bad is relative, with port fuel injection needing faster information than carbureted systems.

Any O2 sensor that will generate 0.9 volts or more when heated, show 0.1 volts or less within one second of flame removal, and pass the two minute heat test is good regardless of age. When replacing a sensor, don't miss the opportunity to use the test above on the replacement. This will calibrate your evaluation skills and save you money in the future. There is almost always no benefit in replacing an oxygen sensor that is good.

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