Looks like you passed the HC and the CO with flying colors.. that looks to me like its running pretty good.
The NOx will be high if you have a bad EGR, bad Cat, or if your truck is very hot.
Possibly the cat is bad, because when those go bad you will fail on the NOx. on my '01 Z28 I had a bad 02 sensor that would dump a lot of fuel in that bank, and it burned up the cat very fast, like within a month.. so if its not running optimally it could have burned up the cat in the last year and now thats why its failing the NOx.
Also i was under the impression that i need to get my vehicle very hot before getting it smogged so it will run cleaner.. NOx goes up the hotter that it is running because it will run leaner.. So if you got it real hot before you smogged it, next time try to get a pre test and don't get it so hot.. since your HC and CO passed so clean, if you try to smog it when its not really hot, it shouldn't fail
those tests and it will bring your NOx readings down.
The NOx will be high if you have a bad EGR, bad Cat, or if your truck is very hot.
Possibly the cat is bad, because when those go bad you will fail on the NOx. on my '01 Z28 I had a bad 02 sensor that would dump a lot of fuel in that bank, and it burned up the cat very fast, like within a month.. so if its not running optimally it could have burned up the cat in the last year and now thats why its failing the NOx.
Also i was under the impression that i need to get my vehicle very hot before getting it smogged so it will run cleaner.. NOx goes up the hotter that it is running because it will run leaner.. So if you got it real hot before you smogged it, next time try to get a pre test and don't get it so hot.. since your HC and CO passed so clean, if you try to smog it when its not really hot, it shouldn't fail
those tests and it will bring your NOx readings down.