2005 Honda Accord 4 Cylinder

mathman32

Hi.
My check engine light came on yesterday. The codes are P0139 (downstream oxygen censor circuit, slow response) and P0420 (catalyst system efficiency below threshold). Here is what I am thinking about doing. I want to replace the oxygen censor and I am hoping that this will fix both of codes since the oxygen censor is connected to the cat. Also, it is WAY cheaper to start here. What do you think?

Mort

I think you're right. How long has it been since you had a tuneup? It may be beneficial to put new plugs in it at the same time.

D-rock

Those oxygen sensors are pretty common to fail, start there and see what happens

Yoyizit

Well, mathman, by the numbers, for this decision to be a toss up,

if the O2 sensor costs 1/10th (way cheaper?) of the catalytic stuff
then
the sensor should be 10x (pretty common to fail?) more likely to fail,
assuming your labor is free.

Let's price out some stuff and see what kind of odds we need for this to be a toss up. The numbers will make things more black and white.
You still may be wrong but at least you had a good reason for your choice.

mathman32

Thanks for your help people. I'm going to change the 02 censor this weekend and see what happens.

Mort - I haven't had a tune up in a while, but I think new spark plugs may be a good idea as well.

D-rock

factory plugs are designed to go around 110,000 miles

Mort

Yeah, and some cars can get 7500 miles between oil changes. That doesn't mean I'd do it.

D-rock

Long life spark plugs can start to get pricey, no need to spend money on something that will have no effect on anything.

mathman32

So the 02 censor has been replaced and the check engine light has disappeared (YES!!!).

ukrkoz

and next thing to do is to pull ECM fuse out for about 15 minutes, to clear all presets off ECM. It will learn now how to drive with new O2 sensor.

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