Hey guys so I bought a 2002 Honda Civic LX from a guy awhile back. Now let me tell you everything that is wrong with it, and what I think some of the problems may be. To begin with, the stock engine was taken out, and was replaced with a rebuilt 2005 Honda VTEC engine. It has a Secret Weapon RAM intake, meagan racing exaust and headers, racing clutch (5 speed manual tranny). Now I live in one of the 13 counties in Georgia, that require emmisions, and this is a problem because my check engine light is on (this is problamatic, for they turn you down instantly if the check engine light is on... The car has a brand new CAT on it. Now the code that is coming up is that the " System Efficiency Below Threshold" (or P0420). The man also claimed to have put new O2 censors in, however the 02 censors (on the outside), are kind of a shiny purple color. Also, I am not sure if when they did the engine swap, if they swapped the ECUs also. So what do you guys think my problem could be? Please help. I am extremly frustrated with this car, however I love it... Anybody got any ideas to what it is and what it is not?

 

Did they do a tailpipe test? If so, are the measured pollutant levels OK? Did you put the new cat on, or is that something the seller told you it had?

The second O2 sensor needs to be moved and wires extended if the car was converted from a DX/LX setup with integral cat/manifold, to the EX system with a separate cat under the car. The second sensor must be after the cat.

 

No they no longer do the tailpipe test in Georgia. I did not put the CAT on, however he did have the receit with the date for both the CAT and the work done, and I have seen under the car, the cat is indeed new... And it has one 02 censor at the beginning of the headers, and an 02 censor, after the CAT.

 

Is it a stock cat or aftermarket? You could take one of the flanges apart to look inside the cat and confirm that it's not just an empty pipe.