so I have tried using the search function, but "02 sensor" won't work as a search term...

My 2000 limited's (58k miles) check engine light came on...shop said i need a new 02 sensor and will cost about $200 (160 for the part 40 for labor)...

my questions
- has anyone done this change, is it easy? (i've heard that it can be a pain)
- is the price quoted reasonable? (they said it should only take 30 mins)

thanks in advance for any help/replys/links

Kevin

Get your O2 sensors from www.sparkplugs.com
It's very easy to replace these.
You have 2, in front of and to the rear of your cat. converter. Do you know which is faulty?
Pre-treat the studs and nuts with PB-Blaster.
You don't want to break off the studs removing the sensor.
Good luck!

It is pretty easy. There is a web site the details this pretty well

http://www.4x4wire.com/toyota/4Runner/tech/O2_Sensor/

The key is to determine if you have 50 state emissions or not. The easy way to tell is if you have two catalytic converters then you have 50 state emissions.

I just changed mine last week - took about 10 mins.

Also remember. Your #1 sensor isnt an o2 sensor. Its an a/f sensor. If you try and put a o2 sensor in its place, it wont run right. Your #2 sensor is an o2 sensor

Make sure you listen to toytech.

Sensor #1 or Bank 1 is the Air/Fuel Ratio Sensor on some models and the #2 or Rear Bank is the O2 Sensor.

They are both fairly easy to replace, but you will want to make sure your sensors are to OEM standards or they will continually throw codes.

Also, the front sensor is much more expensive than the rear, being that it has a higher sense of purpose.

How will you know if your 4Runner needs an Air/fuel Ratio sensor as opposed to an O2 for the front?

Well, I think it has something to do with when 4Runners were being made and the California emissions codes came out. This changed the way they had to install emmissions systems in our Runners.

You can look under the carriage and see.

I made the mistake by ordering an 02 sensor when I really needed an A/F ratio sensor for the front. So i was out big money.

Still have it though if oyu are interested or need it for yours.

Do you have the codes it was throwing? I plan on doing the same thing as you today and was curious to see if you got the same codes

thanks for the link

i don't have the code...


SANT6236... I am going to take it back and ask again which sensor is bad

I just did the front A/F on my '99 SR5 (Cali.) and it was pretty easy. The 4x4 wire link is good but is misleading if you are doing the front A/F sensor on a California or (later) Federal two-cat system. They tell you to disconnect the wire first then pull the sensor. On the two-cat you need to do it backwards: unbolt the sensor, pass it and the wire over the top of the pipe and only then can you get to the connector to unplug the sensor. Likewise install--plug in the wire connector, pass the sensor over the pipe and then bolt it in. I got mine from here.

are in really bad shape, but before I changed my A/F sensor I had read that it was a good idea to order new nuts and you can see why. My check engine light came on and was throwing P0125 and P1135 before I changed the A/F sensor. I disconnected the battery and pulled the EFI fuse then I swapped out the sensor. That cleared the check engine light. This whole thread has everything you need to know if you are do up for the same thing and a search of the engine codes pulled up great advice too. Thanks everybody!

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Have an auto parts store that will read your code (AutoZone does it for free here) & see what it is for yourself. Then at least you know what the onboard diagnostics are saying.

I just troubleshot a PO171 trouble code ("Bank 1 too lean")... Was considering an O2 R&R and further research suggested it might just be a dirty MAF. Had cleaned the MAF ~20K miles ago, but figured it couldn't hurt to rule it out. Did so, pulled both ECM fuses & disconnected the batt. cable (to reset the code) & WALA- trouble code gone & she runs like a champ.

HTH,
Her4Runner

I had the po171 code come up a few months ago and cleaned the MAF and reset the cpu and had no problems for a few months. Now the check engine light is back and it's throwing po171 and po200. I can't imagine it's the MAF sensor again and I would like to get to the root of this problem.

I'm at 100k miles now and it has original 02 sensors as far as I know so I am thinking of changing them and running some seafoam through the fuel to clean any potential gum on the fuel injector cleaner. Any suggestions?

Suggestions:
I wish everybody (not just you) would stop with the '02 sensor'--It is an O2 or o2 (chemical symbol for atmospheric oxygen, sort of) but NOT an 02. This makes searching even less productive than it otherwise might be--for yourself and others who may come along later. Same applies to the DTC's, except backwards: it is P0171 NOT PO171 or po200. I hope this comes off as intended to be helpful, rather than picky.

Please post SOME data on your machine, at least year and engine and Cali. spec or not. You will get more and better help. Putting this in the sig is a good idea.

With that out of the way, if you really have 100K+ on your front sensor, changing it is probably a good idea. I wouldn't do the rear one unless I had a P0420 or other rear sensor specific code. Rear sensors should not affect either the running of the car or either of the DTC's you have.

I would also give the throttle body a good cleaning, just because it is easy, cheap, and might help. Then seafoam it to clean places you couldn't get to directly. Put in the new front sensor, reset the ECU and see what happens. A quick peek at the MAF might be worth it, too, depending on how effectively it was cleaned the first time.

There are still a lot of things that could cause these codes. If the CEL comes back on, post back with the codes, the freeze frame data, and the engine particulars. Freeze frame data is very useful in the case of P0300 and P0171.

I am no expert--I just take care of my own cars--but I'm think I'm solid here. If a pro wants to overrule me or make better suggestions, that's ok.

Thanks for the info Durk. I know it's an oxygen sensor, but never bothered to think about using an "o" or a zero. Considering how this could affect searches I completely agree that it would be great if everyone would use the correct "o" and NOT the ZERO.

It's a 2000 4runner SR5 3.4L (I think the SR5 implies this, but I'm a newb) 4x4 at w/ aprox 100k on it. Bought it at 77k 2.5 years ago and have had zero problems until the P0171. Like I said, I cleaned the MAF a few months ago, no qtip invovled, but I did give a few good long squirts with MAF cleaner. I guess with the current mileage I figure it couldn't hurt to do the pre-cat o2 sensor. This is my first foray into an ODBII car. I've been doing lots of reading on the forum tonight and apparently their is only one o2 sensor pre cat and one a/f sensor as well. Should I replace both?

Considering I've never pulled the plugs on this car, I'm going to replace those tomorrow as well. I read on another post that they are to be replaced every 30k. Seems a bit often to me for a fuel injected car, but apparently I am past due. I may even replace them before I do the o2, but I don't know if that could be a factor playing into this.

You mentioned "freeze frame data". What is this? I'm not sure if my code reader deals with this. I guess is something for me to research tomorrow. I paid $70 for the one I have and I thought it only gave me the code.

No Q-tip ever! But those little wires need to end up clean. Blast away with MAF cleaner until they are.

On a 2000, you can be Cali. or 49state. Cali. has 2 cats, A/F sensor in front, O2 in rear. 49state is one cat, one O2 in front and one in rear. Front sensor is one, or the other, but NOT both. Either case, front tends to go bad first and helps the ECU control the engine. Rear causes codes (mostly P0420), and verifies cats are working. So either count your cats or look at the emissions info plate under the hood to know which you have before you try to buy a sensor.

The OEM plugs are due to be changed at 30K. The waste-spark system wears them out twice as fast, although mine have looked great at 30, 60, and 90K and probably could have gone longer. I'd change yours now because they are due and it is always possible that the actual problem is not doing them any good and that might make solving the issue harder. Then with 100K I'd change front sensor, go here to get the RIGHT Denso number:

URD O2 & A/F sensors

This is why you need to know if Cali. (A/F sensor) or 49-state (O2 sensor)--they are very different. Get 2 new nuts from dealer, 90% chance yours are shot or will be by next change. Buy the sensor from URD, Amazon, or wherever. URD price is reasonable, but not absolute best. No Bosch. Clean the throttle body, if it is covered in yellow varnish you just found your problem. Reset ECU and see what happens.

Sorry--freeze frame data gives you info on what was happening when code was set. Engine RPM, fuel trim, temp, etc. Simple code reader won't get it--a BR-3 and a laptop or a fancy scanner type code reader will. The FSM expects you to have this info available when diagnosing these problems. My BR-3 cost about $100 and has paid for itself 10X +.