I just took my other car into the honda today to get the alternator fixed and soon after I got a call saying I had to fix basically everything on my accord v6. The thing that was buggin me the most was the oxygen sensor that he was talking about and is going to cost me about 300 just to fix it. The guy didn't even know what it does when I asked him to explain it to me, but appearently its faulty on my car. So for all the car guys on this site, can anyone help me out on this? This smells a bit fishy since he had no clue what it even does. well.. thx guy for any response.

 

The oxygen sensor is part of the emission control system. The goal of the sensor is to help the engine run as efficiently as possible and also to produce as few emissions as possible.
The oxygen sensor detects the air-fuel mixture of the engine by measuring the amount of oxygen in the exhaust it feeds data to the engine management Computer which instructs the fuel-injection system to trim the mixture richer or leaner in order to reduce exhaust pollutant emissions.

 

ajkewler,

I believe (am not sure) there are a few kits out there to short out your O2 sensor. I think a few people use them to prevent a CEL when they run a straight test pipe in place of the catalytic converter.

Ask around. this may solve your problem cheaper.

Now the question is, do you really need the O2 sensor for drivability or just for tree-hugging. If you car needs an emissions inspection it won't pass thouh

 

Your oxygen sensor allows your ECU to properly meter the fuel mixture. Most modern cars have more than one sensor, one before and one after the catalytic converter. The second one is simply to notify the driver that the catalytic converter is no longer functioning properly. The first does what islander already posted, and it is definitely necessary, for drivability and performance at anything other than full throttle. Usually (I don't know how it works in an Accord), the ECU operates by using a fuel map to control fuel flow at full throttle, and no longer depends on feedback from the O2 sensor. AFAIK, O2 sensor bypasses, or other methods of simulating O2 sensor input to avoid Check Engine lights, are usually used for the second O2 sensor, so you can run an exhaust system without cats. You still need the first one to function properly, so far as I know.

You might want a second opinion before spending that kind of money. It would be perfectly reasonable to have them fix the alternator, and then take the car to another dealer to get a second opinion, IMHO.

 

Did you have a "Check Engine Light" on the dash when you took the car in? A bad O2 sensor would have activated the CEL. It seems odd to me that you take the car in for an alternator job and they find out that the O2 sensor has gone bad. If they said you have to fix "almost everything" on that car, can I assume that it is an older vehicle? If this is the case, then you should get stuff that is critical fixed and leave anything that is not safety related. For something like an O2 sensor, you should have this checked out by an independent shop. If you do need a new one, you can get an aftermarket O2 sensor far cheaper than what Honda will sell you.
They may make you thing they are doing you a service by checking your car out when you bring it in for something specific but in fact, they are trying to increase their revenue, plain and simple. Unless the car is still in warrantee, which I'm thinking it is not, you should be looking for a reliable independent shop that can work on your car. There is really no need to continue paying a Honda dealer the rates they charge when there are many good alternatives out there. An older Honda is not a unique car and Honda is not the only ones that can do good work on them.

 

Thx for all the replies, I simply wanted to know whether it was a bogus repair job. The issue with the money isn't much of an concern, just don't wanna pay for a make believe service. The car itself is a 2000 model, so its relatively old but not that old. I'm calling the techie at honda world later today to order that 02 sensor. Just feel a bit safer having honda parts installed by honda techs. Thx again for all the replies.

 

The HO2S's on OBDII cars are almost always good for at least 100K miles - I tested mine the other day (95K) and it is still hsowing fine performance - it is measured in how fast it responds and in the voltage outputs it gives.

Premature damage can occur from certain fuel additives and the solvents used in some gasket subsitutues - that is why if you use a silicone type gasket material it should always be labeled "sensor safe". I do not recall where you indicated how many miles you had on your car, but if it s a 2000, you are probably inb the 60-75k range, no?

I agree with Xviper - a bad HO2S will almost always throw a MIL (malfunction indicator light (generic) or CEL (Honda). I think the dealer is fishing for dealers - drop by and ask them to show you on the engine scope or OBDII scanner where the "malfunction" is - I say drop by necause it is not unheard of for unscruulous techs to have a bad sensor laying around that they can loop in quickly - telltale signs would be wrench marks on the sensor hex, or a clean area where the sensor is - it is a dirty part of the car, and if it has not been altered, it should look dirty.

 

Just to clarify, the front o2 sensor(s) detect only the presence of oxygen in the exhaust, not the "amount" of oxygen in the exhaust. The rear o2's are used to detect proper catyletic function as others have stated. The malfunction of the front o2's will cause the car to run poorly and will throw a CEL. The malfunction of the rear o2's will do nothing, but show an MIL. The replacement of either should not be more than the cost of the part plus maybe 10 minutes of labor. This is something you could do yourself without breaking a sweat. Be very suspicious of anybody who tells you otherwise...

 

Hi Road Rage,

Do you know how to test whether the O2 sensor is still good? Currently I'm getting P0141 translates to 2nd O2 sensor heater circuit, I know the sensor is bad, or the heater or circult. How do I do the testing?

 

The oxygen sensor is part of the emission control system. The goal of the sensor is to help the engine run as efficiently as possible and also to produce as few emissions as possible.
The oxygen sensor detects the air-fuel mixture of the engine by measuring the amount of oxygen in the exhaust it feeds data to the engine management Computer which instructs the fuel-injection system to trim the mixture richer or leaner in order to reduce exhaust pollutant emissions.