P0420 - Seems to like me
 

Alright...so its the time of year again where I need to get my cars inspected, and once again my eclipse is giving me some issues.

Same thing happened last year, I was getting this code (P0420 - Catalyst System Efficiency Below Threshold). At one point I ended up getting the code P0140 - 02 Sensor Circuit No Activity Detected (Bank 1 Sensor 2), so we replaced that O2 Sensor and that code hasn't came back since. We managed to get the car inspected after weeks of trying. But not even after I left the parking lot of the inspection garage, my CEL came on once again for the P0420 code and its been on ever since (that was January/February of 2011).

We replaced the following (these are things that might be related to this issue):
Walker OEM Cat
Rear O2 Sensor
Spark Plugs, Wires, and Coil Pack

I looked under the car and there seems to be no leaks what so ever, very quiet. This car is bone stock and I plan to keep it this way, so no mods or anything like that has been done. I also should point out that I don't have much miles on this car, there is only 84,000 miles.

I could go out and buy a front O2 sensor and pray it fixes the issue, but before I jump the gun I was wondering if anyone else had this issue or has this issue? And what was the fix for you?

-TheRock0720

The cat is OEM?
I have seen when front O2 sensor will cause this DTC a few times on lancers and eclipses .
Best way to verify is to look at the live data if you have a scanner capable of it,or you can just try to replace it at your own risk

I ended up examining the exhaust for leaks. There was/is none; very solid. I then installed, for the lack of a better term, "spacers" on the rear O2 sensor and reset the computer. So far so good.

This is what the rear O2 sensor technically looks like now (not my photo):
http://ephatch.com/images/fouler/12.jpg

I believe that my car is burning and leaking oil (you can clearly smell it) so that must be throwing off the sensors thinking the Cat isn't working properly. Hopefully pulling the O2 sensor out of the exhaust system will do the trick until I can attack the oil leak this spring.