maybe it's because you changed 2 cats too many [email protected]!... There is 2 catalytic converters on your pathy... do you have a check engine light.? maybe your O2 sensors are still running in a rich mode...(open loop)...rap633 wrote:I bought a 2001 4wd. I live in Colorado and had to pass an emissions test. It passes easily on everything but Nox. The NO level is over twice the limit.
Has anyone here run into this, and do you have any suggestions.
I have already done basic tune up and changed all 4 Cats!!!!!!!!!!!!!!