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Oxygen sensor--am I being ripped off?

Hi. I have a '96 4runner limited. Several mos ago a light came on on the dash. Turns out it was an O2 sensor (autozone verified after they used their gadget). So I went on-line and noted there’s 2 sensors–one forward of and one behind the catalytic converter. The rear one I figured must be the culprit since it was basically falling off its mount due to corrosion. So I removed it & did not replace it. There was a hole left in the exhaust pipe which I patched with some aluminum and a c-clamp–which worked great–squelched the noise. I also disconnected the battery cables and put them back on. This made the problem light go off, but unfortunatley not for long.

So fast forwarding to present day…I just took the car in to a garage due to my emissions sticker expiring. I did not pass the test of course due to the light being on. I came back a week later to have a new O2 sensor replaced. So I drive the car home and sure enough, the light comes back on. So I look under the 4runner and there is still no rear sensor there–no new one, nothing–just as I’d had it for 5 mos. And no new front one put in either–I obviously know where they go since i’d removed the rear one months ago.

So I was just charged $250 for removing and replacing an O2 sensor. I just called the guy and he swears he did replace and in fact has the part! We’ll sort it out on saturday. Is there more than 2 sensors on this vehicle? I was thinking I was totally ripped off and the guy would blame it on a subordiante but he is saying he has the old part from my car and will show me on saturday—very confusing. My guess was he just disconnected the electric, making the light go off and was hoping it just wouldn’t come back on. But again, he’s saying he has the part off my car!

At a minimum he should have noticed there was no rear sensor there at all, but he made no mention of it. So, are there more sensors on this 4runner that I’m not aware of? If there are they are in hard to reach places—seems at a minimum he did not pursue the path of least resistence. Also, an ebay photo of the part number on the invoice looks like the two sensors I am familiar with.

thoughts? comments?

What engine is in it? If it has a 4 cylinder it should have one upstream & one downstream sensor. If it is a 6 cylinder it should have 2 of each - one for each cylinder bank.

If you want to keep this car going indefinitely do yourself a favor and fix things when they break rather than doing the hack stuff.

Also note that those error codes cannot identify bad parts. I don’t care what anyone at Autozone or anyplace else tells you. There is no code that says an O2 sensor is bad. Its also the case that you cannot disconnect a sensor and hope that this leaves the check engine light off. This will turn the light on - the computer needs info from the sensor and if it doesn’t get it, it turns the light on.

Do you have the actual codes from each of these episodes? The codes will distinguish up from downstream and bank 1 vs bank 2 sensors. It still won’t tell you whether they’re bad or not. But codes that include reports from O2 sensors do tell you which sensor.

The OP does not understand the system but he knows how to suspect a rip-off. This means less work for me.

thanks. I appreciate your response. Mine’s a 6 cylinder limited edition, so it now feels like he is not ripping me off but is guilty of missing the missing sensor right under his nose (which may and may not be the only culprit).

re codes, I have is something stapled to my bill which says P0141 02 sensor heater circuit bank 1 sensor 2…but I’m not sure if thats what he DID work on…or what he SHOULD HAVE worked on or both. I do know my lights back on and a rear sensor is not even attached and was not even addressed by the mechanic.

The one I “hacked” is basically under the passenger side, basically attached to the exhaust pipe, to the rear of the cat converter. Maybe there’s other sensors but they were not obviously visible to me (but i’m only a hack).

As for the hack thing–I can not disagree. It was a Sunday and nothing open and I knew the car would basically sit there not being driven. I didn’t expect the thing to basically fall out. I knew I’d have my day of recokoning with the stiker expiring though and the car is very rarely driven.

You need to keep in mind that an O2 code does not necessarily mean the O2 is bad. “Verified” by AutoZone could be debateable.

Ok - it sounds like the mechanic is incompetent, but that doesn’t mean you got charged for work that wasn’t done. (Of course, I also have no way to say the work was done either).

I would take it to a different mechanic - ask around for a good, local, independent shop. If you’re running around with no O2 sensor at all then there will be a code that would lead someone to check out that sensor and its wiring. That would inevitably lead one to the empty hole in your pipe.

So maybe go back and get your old sensor from that shop to see whether you can be assured that a sensor was replaced. But if your story is all straight I wouldn’t use that shop again.

FYI: the codes that do include direct reference to an O2 sensor will refer to a sensor number and a bank. Sensor 1 is the first one, before the cat converter. Sensor 2 is the one downstream of the cat. Bank one is whichever “bank” of cylinders your # 1 cylinder is on. On one side of your engine you probably have cylinders 1/3/5 and those have their own exhaust manifold. The upstream bank 1 sensor is in or near that manifold. The other side of the engine probably has cylinders 2/4/6. That is bank 2 and will also have an upstream (#1) sensor on that manifold. Then there is a downstream sensor to match each upstream sensor b/c some of what the computer looks at is the difference in reading between the upstream & downstream sensors as a way of telling whether the cat converter is doing its job or not.

I hear you on the autozone thing but again, one of the sensors is not even on the car anymore–its in my garage. So the O2 may not be bad but I clearly have a sensor issue. Cig–I hear you on using a different mechanic and I’ll probably do that, but I might use same because I just think it needs to be set right with the original guy. And to be clear I am not accusing him–recall my header is actually a question not a statement.

Could just be an innocent if incompetent thing. he may have just replaced the wrong one and if thats the case maybe he’ll make a reasonable suggestion as to how to remedy this. I’ll give him the benefit of the doubt but will all depend on how he responds, what he suggests. I do note the part alone was $170 which seems high. $65 to install on top

I have been “savaged” here because of my header. Perhaps the train of thought is I should know better. About my “policy”, my policy is to not get heavily involved into calls from the public to lable a garage dishonest.

I will call a "duck a “duck” when it is obvious to a reasonable degree (meaning if it is pretty much certain that some shady dealing happened, I will get onboard).

Old–glad to know your policy with respect to when you will or will not get involved. Who cares? Why is your involvement or non-involvement relevant? Not sure why you needed to tell us that

problem resolved—post mortem:

So I went back in on Saturday. They hoisted my 4runner up and I was allowed to be right there and point out that there was actually no sensor in the downstream and point out my “hack patch”. With the car hoisted I could see that the upstream was a new sensor–that they’d replaced that one last week, the wrong one. The tech that actually did it was right there and said “my mistake”. So they made it right in about a half hour–put back in the old upstream sensor and the new one into the downstream—no more charges of course.

So I believe it was an honest mistake. I believe the price for the part was too high, but an honest mistake with respect to the installation fiasco. Bottom line I’d use him again but I’d first make sure markups on parts are reasonable or source parts myself and let him (or someone else) install.

You follow up is greatly appreciated. It happens pretty rarely so people are just left wondering.

Let us know when the check engine light comes back on though :wink: