I have a Nissan Altima GXE 1997 and it has 160K miles on it.Recently moved to CA and its failed the smog test.

From the somg results it only failed in HO2 and NO emission. The mechanic replaced oxygen sensors and it failed the No emission now.

WIll replacing EGR value will solve the problem or should i replace the CAT to pass
the CA smog test?

Please suggest me .

I would work with a smog repair shop in order to get the issue corrected. Usually, if you spend over a certain amount, you can get a one year smog exemption. Check here for info: http://www.dmv.ca.gov/vr/smogfaq.htm

I couldn't find the details to get one year somg exemption.
I have already spend a lot for diagnose and fixing the sensors.
The repiar shop mentioned to replace CAT for the car and its very expensive.

Look here: http://www.smogcheck.ca.gov/80_BARResou ... _FAQs.html

Does Nissan Altima GXE 1997 4 cylinder car has two catalyic convertors ( Front and back) or just one?

What are the parts that come up with the CAT kit for this car??

It may have a pre-cat and a cat but I'm not 100% certain. Best bet is to call the dealer and see what they list.