Hello to all.

Just bought a used 03 Eclipse spyder. After about 2000 miles check engine light came on. Error code P0421. Replaced upstream O2 sensor and cleared code. About 100 miles later light came back on. I am reading here that it may be bad Cat or need reprogramming or both. Car now has 90K miles on it. Since I am the second owner am I elegible for recall on Cat & reprogramming at a dealer or is it on me?

Thanks for any help

 

I am assuming you have the 2.4L? Mine did the same thing, what i did to fix:

Purchase a 3/4 inch spark plug fowler at autozone, its about 2 bucks, drill out the hole to 1/2 inch, install down stream O2 sensor to spark plug fowler, then install into exhaust pipe, clear code, good to go!

This might not be the approved method of doing things but it does work, it will also work if you decide to get rid of the cat all together, but I am completely against that

 

What is a spark plug fowler? Is it like a Helicoil? How far downstream did you place the new sensor? Did you pluig the original sensor hole?

Thanks

 

here is a pic of what it looks like



the small hole on the end needs to be bored out to a half inch diameter, this will allow for the "nipple" on the O2 sensor to fit into it, the sensor will screw directly into the fowler and the fowler with the O2 sensor screws into the same spot it came out of




You only need to use one fowler by the way and it is located behind the cat under the car

 

Great pics and info Digital Eclipse,

But the code tells me its the O2 sensor upstream before the CAT. Did you have the same code P0421 ? And did this fix your problem? Will this just put the sensor in a different stream of exhaust and that solves the problem?

Thanks

 

I was constantly getting the same code when I modded mine, so if you do this to the down stream sensor, you should be fine, your eclipse runs okay right?

 

Eclipse runs fine, but I have no modifications ( All Stock )

 

If your cat was bad your car would run like crap, so do the fowler and you will be good, let me know if it works for you

 

Hey digital Eclipse,

I finnaly got around to trying your idea. Installed as you said and CEL has been off for about 1500 miles now.

Thanks for the great info

 

Glad I could help