Originally Posted by Pathale
I have a 2006 LJ. The problem is that it cannot pass emissions. The CEL came on about a month ago and read catalytic converter. After a lot of research my mechanic and I decided to replace the cat. I drove it for 100 miles, and then brought it to the emissions shop. In VA before emissions is conducted, your vehicle must pass an on board computer readiness test. The jeep failed this, and the test said it nwas the cat. So we checked all the o2 sensors and they are all working as they should. Then I ran deadpan through it, everything is running great. I drove it another 100 miles. Took it to the emissions shop, and it failed the oBD test again... At this point I do not know what to do.
There is a difference between a failed emission test and a rejected test because the monitors are not set.
What cat code did you have? P0420,30? Are you not testing because the cat monitor is not set or are you failing due to an OBD II emission related code?
If the cat monitor is not setting there is a reason, the cat, O2's, exhaust leak, drive cycle not complete, etc. Many things can inhibit a monitor from setting. Mode 6 data can be used to help identify the issue.