I've always had good luck with automotive forums, so I thought I would post this question on the Grand Am forum.

I hava '94 GA, with a 2.4 liter engine, with 49k miles. It has been maintained well, and just had a new ingnition coils installed.

It failed NOx during it's inspection. The standard is 1045, but the car read 1573.

It passed HC and CO%.

The check engine light is NOT on. Is there something that I check or change before I take it a mechanic, such as an Oxgyen sensor?

Any help is appriciated.

An inoperative egr system can cause this or a weak catylytic convertor.