Talk:Oxygen sensor

Initial comment
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.

In the Oxygen_sensor section, I question the statement that this type of sensor "is (as of 2006) used in only a few vehicles." Since I make diagnostic software for cars from the Volkswagen_Group (which is the 3rd largest manufacturer in world) I can state with some authority that virtually gasoline powered car they've made in the last 5 years uses a wide-band Oxygen Sensor(s). I do not know whether this is the case with other manufacturers as well. Still, if the 3rd largest manufacturer uses them in just about every car, I do not thing that "used in only a few vehicles" is correct. UweRoss (talk) 22:45, 13 August 2008 (UTC)
 * I agree, this line is utter rubbish. I will remove it now, since its been a while without somebody changing that. Renizer (talk) 17:41, 26 January 2011 (UTC)

How does the heated oxygen sensor give temperature feedback to the ECU so that the ECU can regulate it's temperature?Jksgvb (talk) 22:24, 4 April 2010 (UTC)
 * As far as i know, the heater element is kind of self-contained, in that there's no external control loop for its temperature. The heater element wires just get hooked up to an ignition-switched +12V and GND. I admit i have no clue how it works technically, but i assume the heater element switches off when a certain temperature is sensed. If somebody can shed some more light on this it would be nice to add to the article. Renizer (talk) 17:41, 26 January 2011 (UTC)

Merger proposal
The sensor described in that article is simply a wide-band oxygen sensor. Therefore, it should be merged here, unless the article is expanded with other types of gas analyzers which are used to determine AFR (like CO IR interferometers and Orsat apparatus). --arny (talk) 20:30, 6 November 2008 (UTC)
 * Are you referring to AFR sensor? That article is already very long so I don't think it should be merged with Oxygen sensor. Biscuittin (talk) 13:23, 17 March 2009 (UTC)
 * Then perhaps THIS article should be merged there? This is clearly a duplication... arny (talk) 10:41, 4 August 2009 (UTC)

Uwe is right...volkswagen uses this type of sensor in all gasoline engines from 2000 on. —Preceding unsigned comment added by 92.81.187.91 (talk) 19:03, 1 November 2009 (UTC)

What are the technical differences between the Air-Fuel Ratio sensor and the Oxygen Sensor? Some state an AFR is before the converter and the O2 is after the converter but no physical or mechanical reasoning between the two being in two different places of the exhaust system. Only then could I determine if the two devices should be merged into one disscusion. —Preceding unsigned comment added by Johnbob57 (talk • contribs) 16:43, 11 June 2010 (UTC)


 * Oxygen sensors are used outside of automobile engineering. They are also used by scuba divers to determine the percentage of oxygen in a filled cylinder of nitrox, and as a component of some rebreathers that dynamically adjust the fraction of oxygen in the mixture being breathed. As there are no converters or fuel involved for scuba diving, perhaps a discussion of technical differences belongs in the AFR sensor article. For similar reasons, I would not support merging Oxygen sensor into AFR sensor as if that were the only application. --RexxS (talk) 18:39, 11 June 2010 (UTC)

Various AFR sensors are a subset of and are already discussed at length in the Oxygen Sensor article. I don't think the AFR article adds anything. And, the title AFR should be changed to something intelligible like Air Fuel Ratio Sensor unless the page is deleted.

Normal Operating Temperature Ranges
Great article, but no mention of the operating temperature range of the different sensors. This information would be useful for (people like me) coming here to understand and test these devices. My Zirconia sensor starts to operate at about 400 degrees Celsius. Normal exhaust gas temperatures are probably between 600 - 900 degrees Celsius. — Preceding unsigned comment added by 79.121.186.28 (talk) 08:38, 20 February 2014 (UTC)

Dubious claim about atmosphere via wiring harness
In the section "Titania sensor", there's a claim regarding not requiring access to a reference sample of atmospheric air, in contrast to the zirconia sensors which do:

"While most automotive sensors are submersible, zirconia-based sensors require a very small supply of reference air from the atmosphere. In theory, the sensor wire harness and connector are sealed. Air that leaches through the wire harness to the sensor is assumed to come from an open point in the harness - usually the ECU which is housed in an enclosed space like the trunk or vehicle interior."

Yet O2 sensors that I've seen, and see in images via google, and also the one in this article's lead picture, do not have a sealed wiring harness up to the sensor body. Instead there are individual wires. So access to atmospheric air is simply through some orifice on the sensor body, one imagines. 98.176.1.150 (talk) 19:42, 17 May 2017 (UTC)

Automotive Applications Needs Refocus.
This section is written largely from the perspective of emissions control, which is an excessively narrow focus, and places direct causality where it is not appropriate (possibly a post hoc ergo propter hoc fallacy).

The primary purpose of an oxygen sensor for automotive applications is to determine the state of tune of the engine. One of the benefits of this is the reduction of emissions, but other benefits include increased efficiency and power output.

Oxygen sensors are used to tune engines in performance applications, where emissions are not a consideration. The way this section is currently written, readers would not expect that to be the case. D-qoi (talk) 06:11, 17 September 2017 (UTC)

"Lambda sond" listed at Redirects for discussion
An editor has identified a potential problem with the redirect Lambda sond and has thus listed it for discussion. This discussion will occur at Redirects for discussion/Log/2022 July 26 until a consensus is reached, and readers of this page are welcome to contribute to the discussion. BD2412 T 03:53, 26 July 2022 (UTC)

Proposed merger
The article Air–fuel ratio meter is a complete dog's breakfast, as discussed here several years ago. It can't decide whether it is about wideband O2 sensors or something else. It mostly duplicates information which is, or should be, in this article, although it is very poorly-sourced. Some of the more coherent content from that article should be merged here to bring this article a little more up-to-date with modern technology. If there is anything sensible left at Air–fuel ratio meter about something which isn't simply an oxygen sensor, it could be kept, but I suspect there won't be anything sensible worth keeping. Lithopsian (talk) 15:24, 20 September 2023 (UTC)
 * Agree that a merge is warranted, but perhaps Air–fuel ratio might be a better target. The content of Air–fuel ratio meter is almost entirely unreferenced; of the two references, one is a blog and the other a rather technical manual. I also note that the page has been tagged for poor referencing since 2013, so there has been enough opportunity for improvement. So, I suggest a merge of only the referenced material (or apply TNT!). Klbrain (talk) 07:51, 26 February 2024 (UTC)
 * Merge executed to Air–fuel_ratio. TRL (talk) 03:58, 1 April 2024 (UTC)