2004 Mitsubishi Lancer, code P0421 - how to go about getting a new manifold converter?

Hi there. My car’s an 04 Mitsubishi Lancer ES, 4-cyl, 2.0L. So long story short, my check-engine light has been coming up every now and again for the last couple months with the code P0421, which a shop has confirmed I need a new manifold catalytic converter for (they ruled out any problems with O2 sensors). I’ve had 3 different shops quote me about $1000 to replace the part, about $750 of which is just for the part itself. I’ve done some research online however and see replacement parts for far better prices, in the $300 range if not cheaper.

Should I trust any of these online sources? Which, if any, are most reliable? Do many repair shops allow you to bring a part obtained somewhere else for them to install?

Thanks in advance

Most shops will not want to do business with you, if you want to supply your own parts

Shops make a fair profit on parts and labor. They have to, otherwise they won’t be in business for long.

Any shop will charge you more for the exact same part, versus you buying it online

If a shop does agree to install parts you supplied, they will almost certainly not offer any kind of warranty on the part. there may be other disclaimers as well

If you bring that $300 cat to a shop, and it doesn’t work, that will be your problem, not the shop’s. In other words, it’s up to you to return it and bring them a part that works. But you should expect to pay twice for the labor to install it. After all, they did the job twice

Catalytic converters . . . direct fit, anyways . . . have gotten extremely expensive. I wouldn’t expect much quality for $300. And fully expect that the replacement $300 cat won’t last nearly as long as the original cat did

If I were you, I’d also make sure there wasn’t any contributing factor, leading to the cat’s demise. For example, misfire, excessive oil consumption, overheating, leaking fuel injectors, etc.

Yes. You can trust the online parts.

All aftermarket catalytic converters must meet the EPA’s minimum requirements for performance.

But you have to remember that the aftermarket catalytic converters come with a 2 year/24,000 mile warranty. But they can last much longer than that. Where as with an OEM catalytic converters, they provide an 8 year/80,000 mile warranty.

So the question you have to ask yourself is, do you want to spend the extra money for an OEM catalytic converter and hope the vehicle lasts that long? Or install a cheaper aftermarket catalytic converter that will probably last the rest of the life of the vehicle?

As far as shops installing parts provided by the customer?

Each shop has its own policy about providing that service. So you have to ask.