Nissan Repair: emissions, oxides of nitrogen, nissan altima

Question
I recently had my '94 nissan altima tested for emissions. I passed on Hydocarbons, passed on Carbon Monoxide, I failed on Oxides of Nitrogen. Do you think it's time to change the catalyc converter.  I would greatly appreciate your advice.

Answer
Hi Tony -

It could be, however before you condemn the cat, was the Oxygen sensor (OS) checked?. Sometimes it gives a faulty input to the computer and affects emission levels. Changing the OS will be a lot more inexpensive fix - I hope that is the case!

Hope this helps
calvin