Thanks for the help. Is this problem common with the Sonata as well as the Elantra? I was looking at catalytic converters online but they all kept saying they'd work in any state EXCEPT California which is unfortunately my location. I think the mechanic said it would run over $800 for the CC itself (don't know if from Hyundai dealership) and I guess another $400 for the O2 sensor and labor. It does sound extremely high.

 

I'd get a second opinion first. I didn't know you were in California, yes it is different there. I think they have an extra oxygen sensor in the CC. Why don't you call around there and see how much the parts cost? I'm sure it's a problem with Sonatas too.

 

Okay, thanks again for your help.