I live in Arizona, Maricopa county is one of two counties required by the state to have emissions and I have to take mine in every year. It's a really strange test where they do not plug into the OBDII port for diesels but do on the gas vehicles. If they did plug onto the OBDII connection I think mine would fail with the EGR disabled with EFI. I did however pass the visual under hood and the cat visual, the cat is a Donaldson resonator looks kinda like a cat.
The testing consist of: catalytic visual, under hood visual, CEL visual, throttle test to see if the governor is operational, and a final what they call a snap test, particulate/opacity at WOT with a tube on the exhaust pipe. Goes like this, idle-floor it to the governor let off, repeat 3 times. With all the emissions when I purchased the truck the opacity was 4.6 this year was a 6.6 with a maximum of 40.0. My 82 elephant has passes 80% below all maximum allowables for the last twenty years and all the emissions is intact just plugged..........:woott:
The State of Arizona does have rules regarding people who live just outside Maricopa and commute and work daily into Maricopa then you are required to test...........