The check engine light came on yesterday so i took it to autozone and they said that the cats weren't working at optimal efficiency. I got the car back 2 days ago after putting on a gmmg exhaust (sounds great, btw), jet-hot y-pipe (with cats, obviously), jet-hot headers, ls6 intake and mass air flow. check engine light came on on the second day. other than the light, it's been running great. what could be wrong? do i need to replace the cats or send the y-pipe back? thanks!

 

anyone? i was thinking it might be because increased airflow through the cats is throwing the computer off... i just need to know before i drive the car back to college...

 

my guess would be that the rear 02 sensors that you are using are probably calibrated for the stock diameter y-pipe. If you changed the size of the pipe, it might throw it off and cause it to throw a code.

 

even though you have the jet-hot product, sometimes the cats dont heat up enough with exhaust mods. if you like the performance you have now, buy the sims.

 

Another vote for the O2 Sims. The rear O2's don't serve any purpose other than to tell the computer if the cats are operating properly.

The A/F ratio is determined by the front O2's