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Catalytic converter and oxygen sensor

My 2002 Nissan Altima started making a very loud sound this morning.
I took it immediately to the shop and they said to me that the catalytic converter and the oxygen sensor needed to be replaced, the total cost is 1600 dollars.
I googled both parts and the cost is not even 500 dollars for the items together, am I being overcharged? should i go to another mechanic? I dont know what to do! Im a grad student and i dont think i can afford that amount.

Be sure you’re looking at the right parts when doing the comparison. I tried to attach an “exploded view” drawing, and according to it you have primary and secondary cat converters, the primarys being the monitored converters and being in canisters attached directly to the exhaust manifolds. The price will be expensive, but those are the ones that’ll need changing.

I hope I attached the drawing correctly.

I have never heard of a catalytic converter going bad. All they are is a muffler with platinum in it. Now the Oxygen sensor yes they can go bad. But I do not understand the noise. When my sensor went bad all that happened was my mileage went down.

I would get a second opinion.

There are several recalls for 2002 altimas. Most of them should have been done a long time ago, Don’t just roll in and expect anything for free except running your Nin# on Nissan Net and see if there are any open campaigns. Save gas call the service adviser with your vin# and ask if there are any open recalls first then ask for an appointment to see a mechanic. Cat converter is a 8 years 80 thousand mile part. is a recall site.

Good luck…

Yes, catalytic converters can go bad. Burning oil and other things can poison the catalyst eventually so that it can’t do what it is supposed to do. However, you should check your warranty for the catalytic converter. Emissions systems warranties are usually longer - 8 yrs, 80,000 miles for example. Note that aftermarket cats are often less expensive than the OEM cats, but you should make sure that the warranty on such replacements is for emissions, not just structure. Good luck. I’m looking at a similar repair in my future as well.

Yes, ga_beach, converters go bad.

A catalytic converter is a ceramic substrate in a honeycomb sputter-coated with platinum-palladium, a heavy metal in the rhodium family. When nitrogen oxide (NOx) molecules come in contact with the platinum-palladium, a reaction takes place that breaks the bond and seperates the oxygen from the nitrogen. Passing hot carbon monoxide (CO) can then pick up the now-free oxygen atoms and become CO2.

While a catalyst itself by definition causes a change without itself changing, the problem is that molecular contact must be made between the NOx molecules and the Platinum-paladium. Over time, carbon and other miscellaneous contaminants in the exhaust stream (there’s always some) coats the precious metal, prventing the NOx from coming into direct contact with it. The more of the precious metal that becomes coated, the less effectively it can do its job.

Contrary to some of the “magic bean” ads on the internet, the precious metal cannot be cleaned from the cat converter without reprocessing it and the converter needs changing.

I hope this helps clarify why cat converters go bad.

Take it to a MUFFLER SHOP and find out WHAT is making the noise…What is broken…

They can also become clogged and cause an exhaust restriction.

If yours needs replaced, you may be able to get an aftermarket one a lot cheaper than what you were quoted.