My dads 2001 Park Avenue Ultra has the Service Engine Soon light coming on. The code that keeps being stored is Catalytic Converter performance low. In california the emissions are really goofy. You must use cats certified for use only in california. My question is, is there an aftermarket cat for an 01' with the supercharged engine. One shop said the one for the standard park ave would work another said it wouldn't and that you would need to get one from the dealer. The dealer wants $568 but with the dealer one, you get a kit that replaces everything from the catalytic converter back down to the tailpipes. What should he do?

Move out of California

But seriously, you should thoroughly review the emissions laws, because I know that California is very anti-car, and I wouldn't want to see you with a large ticket (I believe cops carry dB meters and emissions at all times), but then again, I wouldn't want to see you get ripped off.... 570 bucks seems way too much for a cat. Mine cost around 100 installed.

But then again, yours was probably not an OEM Cat.

That price is about right for an OEM Catalytic Converter. I know when the Cat started going on my parent'* PT Cruiser (came with Cali emissions equipment) that we were told there was more than just the Cat that made up the emissions package and that we'd need to have everything replaced to have it done. We ended up just living with the code coming up every now and then til we sold the car (since we are in NY.)

My recommendation would be to research it a little more, and even try stopping at the dealership and discussing it with the service/parts dept. person working. They would be able to give you a good idea at what would need to be replaced. You could also maybe try calling the DMV to see if they can give you any advice or places to get more information on the topic.

You can also try and find a vendor that states the CAT is C.A.R.B. compliant, and I believe that is the certification for California Emission.

CA-legal catalytic converters--even aftermarket--are ridiculously expensive, no doubt.

What city/metro area does your father live in? He may qualify for the Consumer Assistance Program, which, if he fails smog, will pay for up to $500 (after he pays the first $20 to $100) for the new cat:
http://www.autorepair.ca.gov/ftp/pdf...ce_program.pdf

I used this program when my pickup truck failed smog. Sure enough, the bill for the cat and O2 sensor was exactly $599.99 ($100 paid by me, $499.99 paid by the state of Kalifornia).