Ok, here is my dilemma. I failed my no ppm on 25/25 and no ppm on my 50/15, all the the other categories were perfect. Here are the numbers in its entirety.

25/25- Reading - Allowed 50/15- Reading - Allowed
HC ppm- 22 - 132 pass/ 20 - 136 pass
CO%- 0.03 - 0.73 pass/ 0.02 - 0.76 pass
NO ppm- 1734 - 945 fail / 1232 - 1045 fail
RPM- 2384 - 3000 max / 1807 - 3000 max
CO+CO2%- 14.5 - 6.0 min / 13.7 - 6.0 min
Gas Cap passed

Any suggestions? Thanks

 

bad o2 sensor
bag EGR valve
bad cat
bad timing
dirty injectors

could be one of those..

 

The EGR system was designed to cause NOx (nitrogen oxides) to be less in the exhaust gases. Ignition timing has been lowered to lessen NOx, also.
Ensure the EGR system is working properly. Retard the timing a little. The instructions are in the Haynes, or Chilton's, Repair Manual.

 

if the car has over 100k miles, i suggest you do a tune up, fuel system cleaning.
then its up to you if you wanna try the test again or put on a new cat as well before trying the 2nd test.
the front part of the cat (called reduction catalyst) controls the nox emissions and if that part is not working then your nox emissions will increase.

as far as egr, if your car is obd2 then most of the times it will set a code if its not working.