oxygen sensor testing


Old 08-22-02, 09:07 AM
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oxygen sensor testing

I have a single wire oxygen sensor. Im trying to do a resistance test to ensure its working. Im assuming since its a single wire in that it grounds off the engine manifold.exhaust. So in theory I set the multitestor to Ohms and apply one lead to the terminal in and one to the cleaned up body and I should get a reading correct? I am getting no reading with a testor that works ( tested the leads to each other get a reading ). Does this warrant replacement? Just want to make sure im testing correctly.

Thanks for your help-Josh

edit.. im testing it out of the car for convenience
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Old 08-22-02, 09:11 AM
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1 wire O2 sensors should be changed every year as they fill up witih junk and aren't heated and get poisoned fast (or lazy) because of that. Pitch it without hesitation.

But yes, it should be grounded through the body of the unit. Another way to check it is with a scanner and look at cross counts.
Old 08-22-02, 11:10 AM
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I bought a new Bosch oxygen sensor. I tried the resistance test on it as well and I still get no reading? I am putting the positive lead to the inner clip terminal and the negative to the body of the sensor. What am I doing wrong or is the new sensor crap?

option C... can you not do a resistance test on an O2 sensor ?

option D... take a leap of faith and just install the new one and call it a day with a little anti seize?

Thanks again-josh

i dont have a code scanner joe. not used to code cars lol. I like weber carbs.

Last edited by josh1; 08-22-02 at 11:33 AM.
Old 08-22-02, 02:53 PM
Join Date: Jun 2002
Location: Long Island, NY
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You cannot check resistance of an O2 sensor. It is sort of a mini generator capable of producing up to 1 volt by chemical reaction.

What Joe was refering to was voltage and change.. Good O2 sensor warmed up should switch between .2 -.8 volts almost every sec. Bad one will have no voltage, hang at either end of the swing or be stuck with no or very little swing(ie .3-.6)

Old 08-22-02, 05:49 PM
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Thanks I put the new one in. If I get some time Ill go ahead and test the readings but Ive never really had a problem with Bosch products -Josh
Old 08-23-02, 06:47 PM
Join Date: Oct 2000
Location: Livonia, Michigan
Posts: 923
There are two types of O2 sensors commonly used: Zirconia and Titania. Zirconia can be identified as having flutes on the end. Titania has an exposed flat element on its end. Both types can be bench-tested using a propane torch and multimeter.


1. Set voltmeter on two-volt scale.
2. Connect positive to sensor lead; negative to sensor housing.
3. Hold sensor with pliers, heat with propane torch and record voltage. A good sensor must be able to produce 0.8 volt or higher within 60 seconds.
4. Next, remove sensor from heat source while observing voltmeter. Voltage should drop within 3 seconds.
A sensor contaminated with silicon, lead, burnt oil, or antifreeze will not pass this part of the test.
To test the sensor's heater, connect the leads to an ohmmeter. Any ohm reading is okay as long as it's not an open circuit.


1. Connect black and gray sensor leads to an ohmmeter set to roughly midscale (200K).
2. Hold sensor with pliers, heat with propane torch and observe ohmmeter indicator. After a few seconds, the ohmmeter should indicate an ohmic value. This reading will vary with flame temperature.
3. After observing reading, remove sensor from heat. The ohmmeter should register infinity

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