Just came back from Autozone and the reason for my check engine light is P0136 bank 1 sensor 2 mailfunction. I know it is my MIL eliminator, guess one is no good. So is bank 1 drivers or passengers side?
If the MIL came on shortly after your offroad H-pipe install, just give it a bit of time. Some times one of the mil's will be tripped, but later it will turn off again...
If that is the case, I'm just letting you know before you going spending any extra money