Talk:Oxygen sensor
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In re: the Sensor Failures section, I believe the statement, "For heated sensors, normal deposits are burned off during operation and failure occurs due to catalyst depletion" is incorrect. Heated sensors fail for the same reason non-heated sensors do - contamination. Sensor heaters also fail. In fact, more heated sensors are replaced for burned out heater elements than contamination. A catalyst by definition is not consumed in the reaction. I will try to find citation for this as time permits. RoyalDoyle (talk) 07:09, 10 January 2008 (UTC)
I've read a bit of the stuff that people have written about automotive narrow band zirconia oxygen sensors on the net, and from driving my car whilst watching the oxygen sensor output, I suspect there may be some confusion. People seem to talk as if when the mixture is close to the perfect ratio the oxygen sensor output cycles between about 0.2 volts and 0.8 volts and the ECU gets a figure for the exact ratio by calculating an average voltage level. I suspect people are misunderstanding it. How I suspect it works is if the mixture is very very slightly on the rich side of perfect the output goes high, and if the mixture is very very slightly on the lean side of perfect the output goes low. I suspect the ECU basically uses this crude on/off signal to tell it when it's crossed the perfect point and it uses this to calculate fueling; it's continually using trial and error basically, I would guess. I suspect the cycling that the oxygen sensor output does isn't caused by the sensor, but the ECU richening and weakening the mixture. I.E. if a oxygen sensor was held in a steady unchanging perfect mixture the output would never change, much the same way as you don't see the voltage output of a battery cycle from high to low twice a second. Unfortunately I'm not 100.00% certain of this so I can't add it to the main article which seems to have two paragraphs which contradict each other at the 'fundamental understanding' level. The paragraph which is correct probably should have 'contrary to popular belief' or something similar added to it. People talk about counting 'cross counts' in order to tell whether an oxygen sensor is faulty, but if the oxygen sensor is OK I think cross count is basically a function of the ECU software; I.E. just because one car has a test procedure where you rev the engine to 2500 rpm and check that you get at least one cross count a second, doesn't mean that applies to all oxygen sensors on all cars. --Robin Arnold, arny@geek.org.uk, www.ratltd.co.uk, 2nd August 2007
In response to post above: You are correct. A narrow-band O2 sensor in effect simply reads high or low, because it's range of measuring A/F ratio is so narrow. The ECU will lean the mixture until it sees the O2 sensor for that particular bank go lean, then it will richen the mixture until it sees the sensor go rich. The ECU will set a DTC if it richens or leans to a certain percentage past the preset "stoich" duty cycle and the O2 sensor doesn't swing.
Also, a rich mixture is good to protect the engine. However, a lean mixture is best for both fuel economy and power. With the stoich A/F ratio of 14.7:1, being slightly rich means that you're severly lacking in free Oxygen. However, slightly lean means you have plenty of Oxygen to burn up all the fuel (as in the real world no chemical process is 100% efficient). This means you're burning the fuel in the combustion chamber more completely, and therefore getting the most out of the fuel you're using. --Silvapain, Silvapain@gmail.com, 06 September 2007
- Novous 22:57, 11 April 2006 (UTC) It seems like the statement about using leaded-gas oxygen sensors (under Common Failure Modes) in unleaded to "clean them" doesn't fit very well to the rest of the paragraph. It's interesting, but not really backed up very much by the referenced link (it's mostly word-of-mouth), and almost doesn't seem to fit the paragraph (which is on ways they fail, not necessarily maintaining them).
It appears that someone has removed the external reference section from this entry. If someone knows how to add this section back, the original links can be found in the history before 23 April.
Can anyone tell me what the resistance measurment should be on an OXYGEN SENSOR on a 97 THUNDERBIRD EXHAUST. I had the info but lost it some way. How is it measured , from between conection or to case ground cold. Must be done with a digital Fluke I know, can not be read with a SIMPSON VOM, you may blow it up due to the tip voltage on the VOM probes. THanks to anyone that can give me an answer. 4.88.10.134 15:34, 3 December 2006 (UTC)
