O2 sensor

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O2 sensor

Postby gsphunter » Thu Nov 17, 2005 9:39 pm

Hey guys, anybody know how to tell if an O2 sensor is bad?

My check engine light is on and Auto Zone pulled the code. They said it could be my Mass Air Flow, O2 sensor, or fuel injector something. I checked the MAF and it's good according to my Volt meter.

Any suggestions.
Last edited by gsphunter on Sat Nov 19, 2005 5:51 am, edited 1 time in total.
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Postby KCDuckMaster » Fri Nov 18, 2005 6:15 pm

Ok its pretty easy. before you run the engine disconect the sensor and measure the resistance between the signal wire and the ground wire (not the frame). at room temp it should read about 6 ohms.

Reconnect the sensor, start the engine and let it heat up to normal running temp. then back probe the sensors harness measuring the signal wire and ground wire, the sensor sends out a signal to the PCM that can be between 0 and 1v. A low voltage for a lean condition and a high voltage for a rich condition. You want it to be at .45 volts which is a stoichiometric ruel to air ratio. But the meter should swing a little above and a little below fairly consistently.

Find a wiring diagram to find which wire is which and then backprobe the signal wire and ground.

Hope that helps some
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Postby gsphunter » Sat Nov 19, 2005 5:53 am

Sounds good KC. I really need to get it fixed if that's what is wrong. I think it's trashing my gas mileage.
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Postby KCDuckMaster » Sat Nov 19, 2005 11:22 am

Ya, I would probably guess that that is what your problem is. If you remembered what the codes were that were pulled, that would be really helpful. But once your O2 sensors fail your PCM just richens your air/fuel mixture all the way since it is better to run too rich than too lean. So ya your gas milage probably isn't what it could be.
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