i just installed my downpipe and was driving my car with down pipe for about 2 days and today when i was driving on the freeway my check engine light turned on i checked my o2 cencor and nothing is wrong with it please somebody help me?

 

its not that the o2 sensor is bad, its that based on the reading the engine thinks your cat is bad. Get the o2 sensor fix and put it on there. If you still doubt its the cat inefficiency code, take it to autozone and borrow their code reader.

FYI: I had my catless downpipe on for probably 2 or 3 months before I was driving one day and the light randomly came on.

 

Its all got to do with the readiness codes. Every car has an emission system (65 and up) and your ECU has to check everything over once you install a new part (re learn whats changed) sometimes this takes a month sometimes 2 days, just depends on how fast you complete your cars drive cycle, its totally normal when u eliminate an emssion componet, it wont hurt anything but you wont pass emissions because of your OBD2, so get a CEL fixer. I worked at Washington state emissions for 2 and a half years, so its not a big deal until it comes time to test

 

www.gruppe-s.com sells the cel fix for $13.99, which is the cheapest price I found when I was looking for one. Its pretty easy to install if you know how to solder. good luck!