02 sensor in Toyota


Old 08-07-07, 09:02 PM
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Join Date: Jun 2007
Location: NH USA
Posts: 56
Question 02 sensor in Toyota

I have a 98 Toyota Tacoma V6, manual trans. The CHECK ENGINE light came on a few days ago. Went to get a diagnosis this morning, it was error code P0136 - the rear oxygen sensor. They checked the sensor with some graphing gizmo and said that it was indeed faulty. Cost of repair would be $214 total for P&L. He said I should replace this because it could eventually clog the catalytic converter, but it would be ok if I needed to wait a little bit (a couple of weeks, to figure out where I am going to get the $) and that basically my engine might be running inefficiently, burning too much fuel...but that the truck wouldn't just die on the side of the road because of this problem.

So anyways, I get back into the truck after that and the CHECK ENGINE light is off now. They told me it "might" come back on..... Now, if the sensor is truly faulty, shouldn't it come back on right away? I drove it around today and no CHECK ENGINE light came on.

Could it possibly be the sweltering heat we have had here the past few days that caused the light to go on? Or something else???

I don't know much about cars so I am hoping someone will be able to give me a clue about this "mystery". I wish I knew how to change it myself.

Thanks for any help!
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Old 08-08-07, 07:18 AM
Join Date: May 2006
Location: Iowa!!!!!
Posts: 3,687
The code would originate at the sensor so the weather shouldn't create any false readings. I've seen some of those that act up intermittently, but it usually an indication they are within sight of needing replaced. That can go on for some time, though.

I would get the code cleared, either by Autozone, or disconnect your positive battery cable for a couple minutes. Then if/when it comes back on, think about getting it replaced.

There are some additives that claim to clean an 02 sensor, but I have little faith in them.

They aren't complicated to replace, but they can be a headache because of their location and if they are rust frozen into your exhaust system.

Hope this helps,

Old 08-08-07, 08:19 AM
Join Date: Aug 2003
Location: Cape Cod
Posts: 4,320
Ummm...not quite goldie

1)That code means there is a malfunction in the O2 circuit
Not necessarily in the sensor

and B) Those CELs don't just light up only when a specific problem is happening
They often go on and off to let you know the computer has detected something wrong, but's not vital to drivability for now...as in you don't have to pull into the first service station you see...the computer can keep you going for a while

-and then there is III) O2s don't need to be faulty to cause problems, they are "consumables" like brake pads, they wear out (well, clog up is more accurate)

It's conceivable you could have an intermittent short in the O2 circuit
But as your team seems to have checked out the O2/circuit thing, I suspect it is your O2
It could be "faulty", or more likely it's failing...

Your team is correct in that the CEL could go on and off
And they are correct in that it's not vital per say, but running rich like that will hasten the O2's demise, eventually cause serious drivability problems for you, excessive pollution and emissions test failures, and surely is already causing you to burn more fuel (affect your gas mileage)...if not, it will

The heat wave won't cause this code, or a fault in the O2
In fact, they are heated O2s, as they only work when warmed up
Old 08-08-07, 08:47 AM
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Join Date: Feb 2001
Location: SW Fla USA
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That $214 may not be too bad a price, my recollection is that the Toy O2 sensors are a little pricey. Pretty easy to replace though, I think yours has two nuts (10mm I think) that hold it down. Depends on how badly the nuts/studs are rusted.

More info here:

Old 08-08-07, 06:48 PM
Join Date: Apr 2007
Location: Canada
Posts: 401
I had problems with the two O2 sensors in a 1998 Olds 88. I replaced the first one, then the second one went too.

First I tried to use the universal kind to save some bucks. Don't try that. They don't work (at least didn't for me). I had to go get two regular O2 sensors and install those. Then everything was well. O2 sensors can be hard to get at, but with perseverance anyone can replace them, heck I did.

I bought an OBD II diagnostic tool when they were still quite pricey. Now they're fairly cheap. You'll need one to re-set the on board computer after installing new ones. I have used mine several times since buying it and I figure it has paid for itself a couple of times over at the higher price I paid a few years ago!

The on board computer has to relearn the information sent back from the sensors to make fine adjustments to the fuel/air mixture so the car will run as intended. This learning process can last a while (a month is not uncommon). If there is a problem after you install the new O2 sensors it can take a while to find out that there is still a problem.

One of the two good ones that I installed several years ago went again some months ago. I ordered one from eBay for about 20% of the cost of buying one from a local dealer. These things probably cost $5.00 to make and we're charged over $100 a piece by dealers!

When the last one went, I cleared the code with my OBD II code reader to see if the unit was still OK or if it was really bad (I couldn't believe the one I had put in a few years earlier had gone again!) That effort lasted about one month and the Check Engine light came back on. I took out the O2 sensor and cleaned the contact and put it back on to see if that was the problem. Well I thought so after about one month because the light hadn't come back on. But one more month and the light came back on. I then took the eBay unit and put it on and it's been good since. It seems that they fail internally as opposed to at the contacts.

I hope my experience helps you.

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