Took my 05 Gmc 1500 5.3L 145k miles down to get get tested since I now moved to Denver and they require them. I have perform regular maintanence, oil, filters and a recent spark plug change(correst gap). I have no DTC's stored and am sure I dont have a vacuum leak because it idles very smooth. I have installed a SLP CAI and side exhaust otherwise the truck is stock. Knowing I had emissions due I ran a bottle of BG44k thru it a month ago. The problem Im having is: HC 0.2435= pass CO 9.6247=pass C02 519.6231=? BUT NOx 2.0732 is above limits @2.0000
The truck was just getting to operating temp when I got there an im sure my wife filled it up with 85oct gas. Wouldnt I get a DTC from the Cats or O2 if they were failing?

 

I don't if this will help but here ya go.
http://www.car-forums.com/s9/t2590.html
http://en.allexperts.com/q/Toyota-Re...x-readings.htm

 

Excessive NOx is created from high cylinder temperatures, it's often associated with detonation. EGR equipped vehicles with clogged EGR ports often fail for NOx emissions. You could try going through inspection after running a tank of higher octane gas, or maybe have an induction service done where all of the carbon is cleaned out of the intake and combustion chambers. All of the oil that these GENIII engines consume allow for a nice coating of carbon throughout the induction system. Excessive carbon buildup will cause high NOx readings. When I used to do NY state inspections at the Toyota dealership, I fixed a few vehicles that failed for NOx by performing a BG Induction Service and pulling the timing back 2*. Don't shotgun parts at this, your cats won't create high NOx so don't blow the big bucks on them.

Try the higher octane gas first then take it from there...

 

Your 05 shouldn't have egr unless the california emission optioned trucks do. Try driving it for twenty or thirty minutes to get it good and hot before tailpipe testing it maybe. Damm I thought all they did was OBD check and not tailpipe test em.

 

I think that they phased out EGR somewhere around 02, my 02 PCM doesn't support it...

 

Ya tommorrow im going for the high octane treatment. 91 is as high as it goes here in CO but i got some booster an add also some alcohol/water remover. im really thinking i didnt give it enough tome to warm up properly and yes no egr on my 05. I already took a can of throttle body cleaner to the intake once to clean th TB which was filthy though i cleaned it to a shine a year ago when i put in the CAI. My 05 runs like a champ ask my buddies HEMI so I hope its was just my fault with the gas and warm up time. ill add my results when i get a chance?!

 

A smooth idle is no way to judge a vacuum leak.
Your Co looks a little high.
What are the min/max ratings?
If you don't have a EGR and the NOX is high I would suspect the cat(s)

 

Well adding Oct booster, couple bottles of water remover/alcohol and 91 gas with a little longer warm up time my readings improved
HC 0.1945
CO 7.4613
CO2 380.3185
***NOx 1.1206
I knew the smog test is a waste of time, Thanks for the help