flickering lights

First timer here but not the last. My 97 lumina 3.1 car has a problem with lights flickering. My service engine light is on thats how I found this out. The flickering is hard to see if you dont look close but it does. I checked the battery and it is ok so I was thinking it might be the alternator. Can someone please help. Also the reason engine light is on is that AZ told me my c-converter is below standerd. It also said my o2 upstresm sensor was bad and if I replaced that it might be the whole problem but it is not. I was told by someone that if I call a dealership I might be able to get the c-converter replaced because of a 8 year replacement hidden warranty. Is this true? I am in need of advice. Thank you

converter is covered for 8years 80000miles wich ever comes first.
i have replace altenator for this condition before.

First timer here but not the last. My 97 lumina 3.1 car has a problem with lights flickering. My service engine light is on thats how I found this out. The flickering is hard to see if you dont look close but it does. I checked the battery and it is ok so I was thinking it might be the alternator. Can someone please help. Also the reason engine light is on is that AZ told me my c-converter is below standerd. It also said my o2 upstresm sensor was bad and if I replaced that it might be the whole problem but it is not. I was told by someone that if I call a dealership I might be able to get the c-converter replaced because of a 8 year replacement hidden warranty. Is this true? I am in need of advice. Thank you
SHARO23 thankyou for the advice. As far as the 8-800.000 if my car is a 97 this is the eighth year. Is that going to give me a problem with dealers?

thank you for the advice. Also will the dealership give me problems since my car is in its 8th year?