so today i got a custom b-pipe (cat to mufflers) for my 6 speed CLS. It goes 2 1/2 in. all the way through to the stock mufflers, a comptech B-pipe i believe is 2 1/2 from the cat and at the y-pipe being 2 1/4in. Right when i get back to the car and start it up, my check engine light is on. I have a friend who has a friend that was able to check the reason for the check engine light through a computer and it came up saying that there was something wrong with one of my O2 sensors. Why would i have an O2 sensor problem from getting my piping done?? Has this happened to anyone else? My car is running with no problems though. Any input would be greatly appreciated. thanks

 

Probably forgot to hook up to 02 sensor on the install or damamged it. There's one before and after the cat. 02 sensors are located on the pipe you installed, or should be.