My CEL has been coming on ever since I replaced the factory exhaust. I installed aa Pacesetter header, magnaflow cat, magnaflow resonator and a Vibrant cat back exhaust. Once this was installed I would get the CEL. Dealership scan showed a code for the rear O2 sensor. I pulled the negative cable and reset the computer. CEL stayed off for a while and came back. Disconnected the battery again and cleared the light. I have done this a few times. Now here is the funny part. I did a coolant flush and a new thermostat about a month ago and the CEL has not come back since then. Is theis a fluke or has anyone experienced this before. I have read somewhere that the Ethanol in the gas now a days causes the engines to run hotter and that a colder range plug and thermostat will help with performance and stop recurrent CEL problems.


http://i79.photobucket.com/albums/j130/mykeln/mysig.jpg

I've seen in hundreds of modified J's... your high flow cat flows TOO well for the sensors to keep up, so the rear O2 sensor thinks the brand new cat is actually shot. There's a thread like this every once in a while....

While I've never had the problem myself, I've heard it's possible to fix it by putting a spacer on the rear O2 sensor to pull it further out of the airflow... a couple of nuts welded to the bung would achieve this.

It has been 1 month since i replaced the thermostat and no CEL. yet. Very strange how the error code related to the O2 sensor and changing the thermostat and coolant seems to have fixed the problem. A lot cheaper than replacing the rear O2 sensor.

http://i79.photobucket.com/albums/j130/mykeln/mysig.jpg