Will a new Oxygen sensor fix the problem?

[Jack from Charlotte]

My wife's '98 Acura RL V-6 has had a check engine light on. I had it checked at Auto Zone and reset it and it came back on right away. Done this twice, actually. Code is for downstream O2 sensor. This car only has 3 O2 sensors. 2 Upstream and one downstream, below the cat.

So if I change the downstream sensor and have the Check Engine Light reset well that solve the problem? What I'm really asking is it possible that anything else could be throwing this code that I might have to fix .... or have fixed in addition to or instead of the 02 sensor?

Thanks.....

 

[edvanp]

I had a similar problem but w/ an upstream sensor on a Regal GS. Replaced it, had the check engine light reset and sure enough, 100 miles later, stupid light came back on w/ the same code. I checked my fuse box and I had blown a fuse that the sensor was on. Replaced the fuse, didn't even bother resetting the check engine light, and within a 100 miles, the light went off for good. Sometimes it's worth checking the fuse box just to make sure.

 

[ediamiam]

Jack - did you try wire brushing the sensor? I thought they couldn't be cleaned. The socket set I bought from oxygensensors.com has 3 different sockets - I think it depends on how tight the fit is. Shipping is free from them.

If its just a fuse, wouldn't the cel be on all the time?

 

[brianl703]

If the light came on right away it might be a heater problem. Anecdotal evidence suggests that Hondas/Acuras are prone to having the heater in the oxygen sensor go open-circuit, which will cause an instant check engine light, even after you reset it.

What is the specific code that you got?

 

[HondaMan]

Jack from Charlotte,

You are correct in asking your question as downstream issues can many times be related to issues 'in front' or upstream.

Often the deltas from the up and downstream sensors are not correct and then your engine faults the downstream when really there is another problem.

For example if you are running way too rich or for whatever reason have fouled up your front O2 sensors, the delta's for front vs. rear would then be bad ... the computer does not always fault the correct sensor.

To continue this little example, say the front O2 readings are correct and should have told the computer to lean out the mixture, but it didn't happen.. or maybe only one of the front sensors is correct one isn't.. etc etc etc

The lastest factory tech flow through diagram I've gone over (Toyota) was 15 PAGES long in just the troubleshooting of an O2 sensor failure.

All this rambling and it could just be that the rear one has gone bad.

Good luck!!

 

[Jack from Charlotte]

Brian,

As I recall it was something like PO141, which is... "Downstream heated O2 sensor heater circuit fault (bank 1)

So when you say about Honda/Acura... "the heater in the O2 go open-circuit..." Does replacing the sensor cure the problem or is something else involved?

When I had the CEL cleared (twice) it came back on right away. within seconds.

Ed- Thanks for that tip re fuse box. I'll check them all carefully tonight.

 

[Virtuoso]

That downstream sensor is there for the sole purpose of keeping an eye on the catalytic converter. It does nothing for fuel mixture readings (at least that's my understanding on OBD-II cars)..that job is for the front sensors.
Chances are (since it says heater circuit) replacing the sensor should fix the probelm right up.

 

[Matt_S]

I agree with Virtuoso. If the code says "heater circuit fault", the heater in the O2 sensor has gone bad. There is almost no chance in this case that the computer is faulting the sensor for a problem elsewhere in the engine. If the code was for cat converter efficiency or something of that nature, then you could suspect the upstream sensors, but not here. You should definitely replace the sensor the code refers to (downstream, bank 1).

 

[brianl703]

There is the possibility, however small, that the open-circuit is not in the oxygen sensor.

I'd check the oxygen sensor with an ohmmeter before replacing it. The two like-colored wires are the ones connected to the heater. Disconnect the oxygen sensor, and measure between them for an open circuit.

If you measure an open circuit there, the problem is in the oxygen sensor.

 

[mechtech]

The lower O2 has to read different than the upstream one, to show that the cat converter is working. You may have a good O2, but a bad cat.

 

[brianl703]

Bad cat would probably show up as a P0420/P0430 code.

 

[sanitarium16]

If thats the code it is giving you, replacing the oxygen sensor will fix the problem.

 

[1sttruck]

It'll fix the problem if that is what the problem was. If you don't want to check the wiring just replace it, it's a good bet but still not a sure one that it'll fix the problem. If it doesn't fix it use the old one to replace a different sensor as the symptoms now sugget that the old one is good, or check the wiring first.

 

[ediamiam]

Most likely will fix the problem. Since its only a '98, I assume its the original. How many miles on the car? I replaced an oxygen sensor recently. The cel had been on intermittently for the past year, only on the freeway after driving 30 minutes and at speeds from 65 on up. The code indicated the o2 sensor close to the firewall (transverse mounted v6). Went to the oxygensensors.com site and ordered a Denso sensor and socket set. About $55 for the sensor and $25 for the sockets. Kind of a tight fit being on the firewall side, but doable. Afterwards no more cel. Overall mileage has increased a little. You can treat the symptoms by changing the sensor yourself and hope for the best, or take it in to a shop, have them run diagnostics AND change the sensor for a premium price. Your choice.

 

[Jack from Charlotte]

Thanks for the replies. This Acura has 85,000 miles and we've had it 2 years. I'm pretty sure it's the original 02. I've got paperwork from the previous owner and it doesn't show 02 replacement though the previous owner is a friend and she thought she'd had an 02 replaced. She only had service done at the dealer, btw.

1st... I got under the car and the wiring from the sensor that was visible looked good. Very good. I've got no problem changing out this sensor, I just want to make sure it fixes the problem. The CEL is on and the car's due for state inspection this month so I need to get it fixed.

I'll probably buy an 02 sensor socket. Saw them in Auto Zone for $9, I think. Though Auto Zone will loan you one for free with a deposit.

One other thing.... I had a CEL code on a previous car, a '96 Taurus for downstream 02 sensor. Auto Zone ran the code for me. The guy who did it said to clean the old 02 with a wire brush... like a spark plug brush. I did, replaced the sensor and it worked fine for 3 more years with no CEL until I sold the car.

One other thing..... ordered the part through Rockauto.com Great place, good prices and good service..... also here's a code for a 5% discount there.....

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