I have a 2002 Sienna with 143,000 miles, and it spends most of its time in rural Mexico. So, I try to anticipate failures, which as you can imagine is hard to do.
My concern right now is the oxygen sensors. I realize what most do is wait until they have a failure, then take it to the nearest mechanic who can get parts.
In my case, since those sensors are sort of special parts, I am guessing they would have to be shipped in from the US. I am not sure of that, but unless the sensors (mine are California, allegedly) are the same as the 2003 Sienna, they may not have them here.
And, at best, that is a two hour drive or a tow.
Do those sensors eventually fail? One has failed and was replaced some time ago; I think there are three total, not that I can’t look that up.
IF they will eventually fail, I will probably have them replaced when I am back in the States, since I am at least at the half way point on this car.
Any ideas? Thanks.
All car parts fail if they’re worn enough, which happens with either age or mileage. Oxygen sensors are constantly exposed to searing hot exhaust gases, and even though they’re designed for that, they don’t last forever. All you should concern yourself with is whether they will last beyond your ownership of the car.
Everything fails eventually. That said, yours may last for some time yet. Please be aware that even when they do fail, it will not stop the car from running well enough to get where-ever you need to go. No need for a tow.
Like 900 miles, or like 50 miles?
In my case, I hope to go another 7 years and 140,000 miles with this car. If they are not likely to last 300,000 miles, or better said, if the odds of that are well under 100%, then it probably makes sense to just replace them, and keep the old ones here in Mexico. This involves hoping the new ones also last 140,000 miles.
I realize your answers are general, though that is all I expected. But, my interpretation of the answers is I might as well put new ones on instead of hoping there is no failure while I am in Mexico.
I know most people wait until stuff breaks, but when there is a long, unreliable parts chain, it changes ones perspective. If a part is likely to fail before my expected use is ended, and I am half way there, then it makes sense to replace at the half way point, and keep what is essentially still a usable part as back-up.
My views are probably biased by 31 years working on high-rel avionics. We had equipment out there working well for 20 to 30 years. There was an overhaul list for each product, and there were times when an agency would tell us to do the overhaul list, which meant replace all items which could wear out, as specified by the design engineers during original design. That gave them the reliability they wanted/needed, without risking missions because of waiting for the failure itself.
On a good car, there aren’t that many things like that. Light bulbs, which started going bad at 85,000 miles or so, so I replaced them all. Battery, which I usually replace at 5 years. Tires when tread gets low, though I wipe out around a tire a year here, so that messes up planning. I will replace my 7 year old spare when I get back to the States because of the new claims on old tires.
The only other things I can think of is the cat convertor, and the O sensors. I replaced the charcoal canister this winter, there was a strange failure, which I finally concluded was in the canister, that is a drivable failure.
The transmission is allegedly famous for a bad O-ring which causes clutch slipping whatever that means, I am trying to find out if that is also drivable (30 mph to the border, yes, I can do that. IF door handles fail, I can crawl around till I get back.
I think exhaust is not a big threat, nor CV joints.
Anyway that is why my thoughts are as they are, on O sensors. Thanks.
All oxygen sensors will fail eventually from contamination. Too many subatomic collisions will eventually ruin them. They sense only oxygen ions which usually pass through the sensor. Whatever they do, they will all fail some day.
Like 900 miles, or like 50 miles?
More like 50 miles to 150,000 miles.
Since the car is fully drivable post failure, this is one I would wait until the next failure.
Also, oxygen sensors are not considered special. Especially for a 2002, any auto parts store carries them. These are just as common as brake pads, spark plugs, and wheel bearings. Believe me, there are more parts on this van that will render it undriveable before the oxygen sensors give.
You can buy universal Oxygen sensors if you want to save a few bucks and you don’t mind connecting the wires.
Some Oxygen sensors are indeed special. The California version, which mine is, use a very special sensor. On the Sienna club, there have been people reported major problems with standard sensors in those slots. It really messes up the computer control, and I think one person believes he wiped out his cat converter with the wrong sensor.
However, I am in rural Mexico, which is the real reason this is a problem. If I were always in McAllen, this would not even be present on my radar screen. “Any auto parts store” does not exist within maybe 2 or 3 hours. and it isn’t going to have much for a Toyota.
I finally can find replacement batteries. Aurrera only 1.2 hours away sometimes has 24F batteries, which means one less worry item, though that is also not likely to fail soon.
I am well aware it is not a real good idea to have a scarce brand auto. If I had unlimited funds, I would buy a Mexican F-150 dual cabin truck, but I am forced by economic realities to try to use what I have as long as I can.
Believe me, there are more parts on this van that will render it undriveable before the oxygen sensors give.
Now, we’re cookin’. What parts are they? 
See comment above. California system uses very special sensors, and those who have tried substitutes have reported serious problems.
Thank you. Thank you. Thank you. This is the information I was seeking with the original posting. As I have said, the issue here is the geographic location where this car is used. IF a part fails here, the cost goes way up, and if it is PROBABLY going to fail eventually, it makes sense to replace at the halfway point, rather than have it go out at totally unexpected times.
Sensors tend to last somewhere between 100k and 200k miles depending on operating temperature, fuel contamination, and how sensitive the car is to sensors that are getting old and responding slowly.
OBDII cars (since 1996) have either two or four sensors, from what I have seen.
Generally, the front one(s) fail(s) first, but I replace them all as preventative maintenance when one starts to fail.
As others have noted, a car will run without an oxygen sensor. However, when a sensor gets so bad that the computer ignores it and switches to “limp home” operating mode (check engine light will be on) the car runs rich. That will heat your catalytic converter more than normal and it will devastate your gas mileage. That is important when you are driving across long stretches of desert where there are no gas stations.
I’ve driven two seperate cars on failing O2 sensors for well over a 1000 miles each, probably even closer to 5k miles. O2 sensor failure will not just cause your car to stop running, it will just not run very well until it’s fixed. You’ll run a little lean or rich and use up more gas, that’s all.
At about $200 US each, arbitrarily replacing the oxygen sensors is expensive “insurance”. Your Sienna probably uses wide band oxygen sensors----nothing more “California special” than that. Any mechanic who isn’t aware of wide band oxygen sensors (and how they operate) is about 10 years behind in his car knowledge.
If you must have the “insurance”, take a front and a rear oxygen sensor with you, in your luggage. http://www.autozone.com/N,16100117/shopping/partTypeResultSet.htm
It’s your call. An O2 failure will not cause the engine to quit. The typical symptom I have seen is a drop in fuel economy ( 30-40% ) and a check engine light. You could drive back to the states to get a replacement, or wait for one to be shipped.
If the situation above is a problem, replace the sensors on the exhaust manifolds only, since they acually control the fuel mixture. The O2 sensor downstream of the cat only monitors the cat’s performance.
If a bad sensor does not hurt the cat converter, that is important information. Some folks thought it did. I assumed running rich would overheat the converter, and before too long burn it up at great expense. Since there is not universal agreement on this issue, I will investigate other opinions elsewhere.
I don’t know about wide or narrow band sensors. All I know is when they look up my VIN, they can tell me it takes special sensors, not universal ones, but a very precise, expensive part number. The non California uses a much cheaper sensor.
The expensive insurance comment. Um, let me see. Manolito said they fail usually before 200,000 miles. I do know the first one failed some time ago, which agreed with that prediction, and is why I am thinking about the other two (Sienna has three, I just looked it up in the shop manual.) I plan to drive this car 300,000 miles unless it’s wrecked first.
So, odds are good I WILL be replacing those sensors, right?
The only question is WHEN.
Will I replace them at my convenience, when I am within five miles of a place that can get the right part, with no errors, and an experienced mechanic? Or, will it go bad when I am hundreds of miles from service, or a number of day’s wait for a new part, and at a much higher price plus shipping? And, as yet undetermined results for the converter.
I realize most people in the US have always thought in terms of REPLACE IT WHEN IT BREAKS. It is a cultural norm, based on the easy availability of parts almost anywhere in the continental USA. It is especially relevant when one is close to home.
When one starts driving from, for example, from McAllen to Virginia on a regular basis, not to even mention to rural Mexico, it is necessary to anticipate failures, a concept which requires a “cultural shift”, and frankly many people cannot easily step outside their culture.
In this case, if I replace them now, they will probably last as long as I use this car. Yet, in the end, the total cost will be approximately the same. No, wait, if I let them go and they fail in an inconvenient place, the cost goes up, not only financial but nuisance. And, if there is risk to the cat converter, the cost doubles or triples. Gosh I think this is a no-brainer, and I thank Manolito for that information.
I went through this three years ago on light bulbs. Aware of what law enforcement is doing these days, with the blessing of judges who violate their constitutional oath, I wanted to replace all my external light bulbs before they failed. Boy, did I get trashed out. I was told light bulbs never fail. I was told they would last longer than I would have the car. Etc. I was really mocked for my foolish attitude.
The hi-stop light went out at 85,000 miles. 
Fortunately I caught it, not the cops. I promptly started replacing all external bulbs, and from now on will do that every 75,000 miles.
Not much later, a California attorney posted on another message board that California law enforcement had started treating a bad bulb as a moving violation – a significant fine with court costs; reported to driver’s license people and insurance people, the same as speeding et al. As far as I am concerned, though I respect the right of others to name their own risks, light bulbs should now be replaced on a schedule basis just like changing oil and tranny fluid. The cost of all bulbs on the car is less than a modest fine and court costs, not to mention cops trying to steal your car on trumped up charges.
My original question was how long the sensors lasted, if they eventually fail, then I would replace now at the halfway point, and bring the old still-working sensors here in the house in Mexico. While I certainly understand those who wait until something breaks to replace it, and respect that decision, that is not workable for me.
I’ve NEVER had to replace a O2 sensor on any vehicle I’ve owned. 3 of those vehicles went past 300k miles. Never saw a decline in gas mileage or performance.
I did more serious Googling, and discovered that some experts view new oxygen sensors every 100,000 miles as standard PM.
Also, the general consensus was running rich with a bad sensor WILL overheat the converter and it will fail.
A bad sensor should be detected and cause and error.