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Oxygen sensor help please Forums > > Oxygen sensor help please Oxygen sensor help please
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Old 09-26-2007, 07:38 PM
greenpinhead86
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Default Oxygen sensor help please

On my 2000 nissan sentra i have been having many problems and i'm testing the o2 sensors with a scope and i'm not sure what the biased voltage should be. im getting very wierd readings and i'm not sure if its rich or lean or what. so if someone knows its range please tell me. i think its something like .2(lean)-1.25(rich) volts. help....
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Old 09-27-2007, 02:06 AM
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mpe235 mpe235 is offline
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Take a look at the sensors. They crack around the top of the sensor.
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Old 09-27-2007, 05:48 PM
FieldRun
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I have a 2000 Sentra with a 1.8, QG18DE engine. The bias voltage on the O2 sensor is approx. -0.5 volts and according to the manual it must go below 0.3v (lean) and above 0.6v (rich) and must not exceed 1.0v. The output must cycle at least every two seconds at 2,000 rpm. See it on a scope may be a little tricky, but very do-able. Don't bother trying to measure O2 sensors with an analog voltmeter since it will load the circuit down and you will not read any voltage. You can take readings with a digital voltmeter. Keep in mind that according to manufacturers, O2 sensors generally only last approx 100,000 miles. They get sluggish, contaminated from silicon RTV, and sometimes they have a full failure. Generally it's the front sensors, not the back sensors. Prior to spending the $100 or so for each sensor, make sure something else is not causing the problem. Complete trouble shooting tests and procedures are in the manual (EC section) and you can download it for free on this website. Good luck. Let us know how you do with the problem.
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Old 09-27-2007, 08:49 PM
greenpinhead86
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That is some very valuable information you provided. Thank you very much,

Today before i read your reply I did hook up the 02's to a single channel scope and went through the four of them. both sensor 2's (bank1 and 2) were reading lower voltages around .3 most of the time. this of course indicating a lean mixture. but since these are the post cat sensors its a little tricky to tell. upstream sensors 1(bank1 and 2) were responding quicker but were still around .3 volts. (meaning engine was indicating lean more often then rich) with a new MAF just recently installed i'm not sure if the engine believes its getting less air then it really is. sounds like another test for tomorrow...

I will keep everyone updated even if you dont care.. haha.
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