Any ideas on what I should check?
My check engine light does come on about 75 percent of the time when i am on the highway for a few minutes. After running a code check, its something to do with the EGR system.

 

3 things come to mind, first pull the codes, im pretty sure you will find its a 32, egr problem causing the light to come on. GMs have plenty of problems with the egr system, the valves & solenoids going out are quite common.
2, check the timing. too much or too little can jack the NOx up.
these 2 things have a big effect on NOx.

3, you may be just alittle lean.
once you have checked these & have them right, i think you will be fine, if not then maybe a carbon deposit build up in the chambers or a cat thats not taking care of NOx as is should but i
feel your cat is probably fine because your CO2 looks good.

pull the codes & post back what you find.

 

Pulled the codes. Got the EGR one, and one other one I forgot off the top of my head (something to do with VATS, which is working great.... )

 

im pretty sure Trickster or Vader has posted up on the boards somewhere the procedure to diagnose code 32, that is where your problem is going to be at as the EGR system is the main component outside of engine design to reduce NOx, third is the cat.
once you get the EGR system going i don't think you will have any other problems as far as getting it to pass emissions, but there is the possibility that something else may show up afterwards.




for after you get the inspection done,..
the other code, i think the VATS code is 46, shows somewhere in the last 50 starts or so the ecm saw something with the VATS, was there a time when it didn't want to crank or would crank but
not start & run?

 

Hmmm like 8 or 9 months ago (I dont drive it that often).

 

might wanna get a gas cap...

 

I do have a gas cap. I own the emissions testing machine and dyno. I did the test in training mode, where a cap is not needed...

 

sorry i was unaware of that

 

Well, I replaced the EGR valve and O2 sensor and put it back on the dyno. Originally I had a reading of 1078 NOX but 879 is the limit. After testing, NOX showed about 521. CUT THE NOX IN HALF! Everything else was pretty much the same as it was the first go around.

 

Get a gas cap you goober!

 

Thanks but read the messages above you and notice that I said I own the dyno/tester and decided not to do a gas cap test and therefore it shows that I dont have one.

 

it' running clean for sure. i think it will pass without the cat now, at least mine does even with the EGR not working right & well over 50000 miles on the plugs & about 20000 on the last injector flush & 4000 miles on this oil change.



i was wondering,........ did you pay yourself the dollar?

 

Pass with both cats off? HAha then I would flunk CO2.

Never noticed the $1. It was in training mode so it never went through anyway.