So I failed our gov't emissions testing on the NOX by nearly 4 times the limit, and I was very high but a pass on the others compared to average readings for this vehicle. Does anyone know anything about diagnosing this stuff? I am thinking 02 sensor, but wouldn't that throw a code? I have never had a code come up since I bought the truck last year (would an old code still be stored in the little black box?). Anyway here are the results in g/km if anyone can tell much from them. I guess you multiply by 1.6 to get g/mile if thats what you guys use down south. maximum vehicle reading average Hydrocarbons 0.99 0.6756 0.1655 Carbon monoxide 12.43 9.9628 2.6518 NOX 1.55 5.3381 1.4807 I guess I am not alone in failing NOX. The average reading for NOX on this vehicle is within .07 of a fail.