O2 Sensor Lifespan

[HondaRD]

With costs of fuel on the rise I can only wonder of ways to increase fuel efficiency. This led me to ask how long does a typical OEM oxygen sensor last? How do you know it is not working per spec? I wondered about this and then hit the internet to do some research on the subject and the interesting thing is I did not find a whole lot except that people automatically assume they need a new O2 sensor when their car fails emissions or the check engine light comes on and when they do replace it, they still have the original problem. I read that some of the symptoms of a bad sensor is sluggish performance, poor fuel mileage, and failed emissions. However, all of the places I read this was from sites that either sold O2 sensors or has affiliation with a company that does.

For me, I own a vehicle with 135,000 miles on the odometer and still have the original Heated Oxygen Sensor (OEM by Denso). No check engine light has ever come on throwing a code for the O2 sensor circuit nor have I ever failed emissions (However my NOx was close to the limit last time I ran emissions). So what I am left to ponder is whether or not I should go ahead and replace something I do not know will show any improvement or benefit and end up costing me $70 to learn a lesson. Everyone I talk to tells me I should replace it every 50-70k miles, but my manual does not indicate anything about it even at 120,000 miles and I am led to believe that modern O2 sensors are like today’s engine oil in that they last longer and perform better than their older counterpart. Others tell me that an O2 sensor react slower over time and could operate outside of spec and still not throw a code.

Does anyone have any knowledge on this subject? Has anyone who replaced theirs noticed any improvement when replacement was not necessary by means of check engine light or high HC or CO levels? I figure if I can save just 1 mpg I could buy a house since I am paying close to $2.50 per gallon. (Yeah I know, I should not complain until I am forced to buy gas in Europe).

 

[Seth_TJ]

First of all we aren't in Europe, so screw them on this. I am paying $1.98 for gas and that is too much.

I replaced my upstream at 50k and I have never replaced my downstream and I am at 75k. I just bought a new one though. Bad part is my exhaust manifold cracked for the 3rd time (3rd one I've had on it) and I think it probably ruined my upstream oxygen sensor and the $100 cat. converter. Also i'm getting like 13mpg. Screwed up my whole Jeep.

Any way back to your question. If you check your FSM it may give you a way to check it with a multimeter. I will check mine and see if it gives a procedure like it does for every other sensor.

 

[cryptokid]

i am not sure about obd1 but on obd2 cars the o2 sensor is monitored by the computer and if it ever operates outside of its preset limits the computer will throw a check engine light indicating what is wrong, weither the o2 is reading high, low, not at all, it will even tell you if the heater element is bad.

so, it is useless to replace the o2 sensor on a obd2 equipped car if the computer isnt throwing an o2 related code.

by the way, my car threw an o2 code out at 64K miles indicating the o2 heater element was bad. i drove it around for a couple thousand miles like that and finally got a new sensor, the code went away. my mileage never changed.

 

[JHZR2]

to really check, you need an oscilloscope to see the very fast change. You can also use a good multimeter, but the process is not that simple. Apparently if you disconnect it the wrong way, or do something wrong, you can break the sensor. That said, any good manual will tell you the fluctuation range and the centerpoint for operation.

If your mpg hasnt dropped, I wouldnt worry about it. If it has dropped, check it. If your CEL comes on, use a scanner (the proper one) and determine the actual problem, or take it to a dealer to do it right.

My father's toyota previa has both original O2 sensors at 10 years and 180k miles. Still deliers 23-25 mpg.

JMH

 

[HondaRD]

Thanks for your input fellas.

Seth_TJ: Sorry about your Jeep. At least your cat converter isn't $300. $100 is not a bad price but three manifolds? That’s ruthless!

Cryptokid: You are right about the ECU monitoring the O2 circuit but it does so just like the OBD-I cars equipped with only one sensor. The secondary sensor located downstream the cat only monitors cat converter efficiency from the data I have seen working on honda's and toyota's and does not directly effect A/F ratio as the primary O2 sensor would but don't quote me on that.

JHZRS: I like what I hear (since it gives me hope that I can save my money)

I have read the FSM as previously suggested. A multi-meter would be required but as stated before, it would seem an oscilliscope is the only way to go and I don’t have one

.

 

[pitzel]

quote:

---

Originally posted by HondaRD:
Does anyone have any knowledge on this subject? Has anyone who replaced theirs noticed any improvement when replacement was not necessary by means of check engine light or high HC or CO levels?

---

When I replaced my O2 sensor in my 3.1L V6 in a 1992 GM car, I went from approximately 525km/tank before the fuel quantity warning light went on to over 650km/tank. The car also stopped smelling 'rich' when I'd leave it to idle on my driveway for a few minutes.

The original sensor, fitted at the factory, had 64k miles on it roughly when I replaced it. Car now has 67k miles on it fuel efficiency consistently beats EPA spec by a wide margin on the highway.

I should also add, I changed the O2 sensor on my own initiative, and definitely not to correct any Check Engine Light or driveability concern.

 

[friendly_jacek]

quote:

---

Originally posted by HondaRD:
I have read the FSM as previously suggested. A multi-meter would be required but as stated before, it would seem an oscilliscope is the only way to go and I don’t have one

.

---

If you have an OBD2 interface (50-200$) and software (free), you can see the O2 sensor output in your laptop or palm pilot.

 

[brianl703]

The O2 sensor degrades in a linear manner. The check engine light is a binary device indicating (among other things) pass/fail of the O2 sensor monitor test.

Since the O2 sensor degrades in a linear manner, how much has it already degraded when the light comes on indicating that it has failed the test?

On new OBD-II vehicles the light will come on when your engine starts to misfire. Does anyone wait to replace the sparkplugs until that happens?

 

[Virtuoso]

brianl703 hit it on the head. Your o2 sensors will get old and slow before the throw a code; witch will affect your gas milage. I replace mine between 80-100k. I bought my SHO @ 103k miles and it was already throwing a O2 code. My old SHO was throwing codes already when I got it at 130k. However my old turbo Shadow wasn't throwing codes at all at 200k, and it seemed like it had the original sensor. New one upped the gas milage a bit though.

 

[brianl703]

If you build a circuit that acts as a low-pass filter, and put it between the post-cat (downstream) sensor and the ECU, the ECU will not turn on the check engine light even if the cat has been completely removed.

In other words, under normal circumstances, the downstream O2 sensor switches slower than the upstream sensor.

The purpose of the low-pass filter is to make it appear to the ECU that the O2 sensor is switching slower than the upstream even when the cat has been removed.

Schematic of an "MIL Eliminator" (what this circuit is called and sold as) here:

http://www.cougardb.com/howtoshow.php?howtoid=8

This device probably not legal for sale or use on pollution controlled vehicles and all of that.

 

[JustinH]

right. On late model fords the downstream sensors are only "cat sniffers", they do not serve any other purpose.

My 98 f150 is throwing upstream sensor lean codes now, and i'll just replace the two front sensors.

It threw o2 sensor codes at 50k exactly, and i'll replace them next week. Getting some slight pinging up high now, so i'll keep the revs down low until i swap them out.

JH

 

[Gary Allan]

quote:

---

Cryptokid: You are right about the ECU monitoring the O2 circuit but it does so just like the OBD-I cars equipped with only one sensor. The secondary sensor located downstream the cat only monitors cat converter efficiency from the data I have seen working on honda's and toyota's and does not directly effect A/F ratio as the primary O2 sensor would but don't quote me on that.

---

Sorry ..I quoted you on it. That is only one element of the dual O2 sensor function. That is, when the computer sees identical read outs from the upstream and downstream sensors ..except for a delay ..then they know the cat is a non functioning item (source 99 Jeep TJ FSM). You now get O2(1) and 02(2) codes depending on which one the computer figures is not functioning properly.

 

[Matt_S]

quote:

---

Originally posted by brianl703:
If you build a circuit that acts as a low-pass filter, and put it between the post-cat (downstream) sensor and the ECU, the ECU will not turn on the check engine light even if the cat has been completely removed.

In other words, under normal circumstances, the downstream O2 sensor switches slower than the upstream sensor.

The purpose of the low-pass filter is to make it appear to the ECU that the O2 sensor is switching slower than the upstream even when the cat has been removed.

Schematic of an "MIL Eliminator" (what this circuit is called and sold as) here:

http://www.cougardb.com/howtoshow.php?howtoid=8

This device probably not legal for sale or use on pollution controlled vehicles and all of that.

---

You can get these pre-made for most vehicles on the various performance/aftermarket racing sites. They're sold for "off-road use only". Yeah right! It's common for people to replace the cat with a piece of straight pipe, minus the rear O2 sensor and put this device in it's place.

 

[BlueOvalFitter]

Ok,correct me if i'm wrong; I was told by Ford techs (I own a 97 F150) that if it aint broke,dont fix it,referring to the sensors.But if it will help my gas mileage,ide change them.But,i'm still not totally convinced they slow down over a period of time.Either that or its the $50.00 a piece price tag i'm afraid of!

 

[davebarnum]

Originally Posted By: Seth_TJ
First of all we aren't in Europe, so screw them on this. I am paying $1.98 for gas and that is too much.



Upset about $1.98 per gallon of fuel.

Man, those were the days.

 

[01rangerxl]

An O2 sensor is kind of an expensive part to preemptively replace in hopes of chasing marginal MPG gains. If the sensor is far enough out of range to really affect fuel economy, it's going to throw a code.

My truck threw an O2 sensor code just past 100K miles...literally, it was within 100 mi after crossing 100K. Absolutely no change in performance or fuel economy, definitely no misfiring or anything like that. Threw in new direct fit Bosch sensors and without even clearing the code, and the CEL went off the next time I started the truck. It's going to vary some by vehicle, but in the case of my truck I have found that the truck's computer figures out that something is amiss LONG before I would on my own. The times it has thrown a CEL there has been no discernible difference in how it drives.

I like to throw money at maintenance too just because, but O2 sensors are one thing where I just wait for the light.

 

[Smokescreen]

On any vehicle I have ever owned, I have never had an O2 sensor fail or even had a check engine light for that matter. I have never gotten rid of a vehicle that had less than 150,000 miles on it either so none of them were spring chickens.

 

[supton]

I had an O2 sensor fail, after 251kmiles. Turbo blew, and while I didn't think it dumped that much oil into the exhaust, apparently it was enough to make the O2 heater circuit go open.

 

[Vikas]

Originally Posted By: davebarnum
Originally Posted By: Seth_TJ
First of all we aren't in Europe, so screw them on this. I am paying $1.98 for gas and that is too much.



Upset about $1.98 per gallon of fuel.

Man, those were the days.


Somebody will bump this thread in another 5 years and today's $3.59 price would look like a bargain!