The car is ten years old, and I had to replace the catalytic convertor for $1200. It's supposed to last the lifetime of the car. I guess they got a bargain from some Chinese supplier. It started to cause the Check Engine light to light up periodically over a year ago, then recently stayed on and it would not pass inspection. As I said in another complaint about this car, I drove a 1985 Toyota Camry that I bought in 1989 for over 20 years. I sold it with 325,000 on the clock, everything worked, original engine and clutch, working A/C, AND THE ORIGINAL CATALYTIC CONVERTOR. My 2000 Toyota Sienna van also has THE ORIGINAL CATALYTIC CONVERTOR.

Take that Nissan.

I just bought my car a few days ago. I was driving home from the dealer when the service engine soon light came on. I checked the manual and it said to make sure the gas cap was tight and that it should turn off after a few trips. Well, it didn't turn off. I took it over to a local auto parts store and had them read the error code and it came up with P0420 Catalyst Efficiency Below Normal (Bank 1). My car seems to be running ok, or at least I think it is.

I did a lot of searching and found most people say the dealership will charge $1000 for parts and labor to replace the catalytic converter, but I question is that really the problem?

Someone mentioned that the error could be caused by: -
Exhaust pipe leaks -
Intake air leaks -
Fuel injector(s) -
Fuel injector leaks -
Spark plug(s) -
Improper ignition timing

If it's none of those things, perhaps it's the O2 sensor(s) that needs to be replaced.

It doesn't seem like something that needs immediate fixing since it doesn't seem to be affecting performance, which suggests to me that it's likely not the catalytic converter and is actually the sensors or something else.

My service engine light went on. I took to an auto repair shop. They replaced two sensors with a total cost of $400.00. I inquired why so much and was told we only use dealer parts when it comes to sensors. We don't use after market parts because we don't want to keep replacing parts. I went to closest auto dealership who disclosed to me that my invoice for the work displayed were high priced aftermarket parts With the work completed and getting my car back the next day the engine light went on again. My repair shop told me the catalytic converter needed to be replaced.

I read on repairpal.com of all the people that have experienced the same problem with Nissan Altimas and the catalytic converter. I can't understand how a recall wasn't done with all the complaints. Many, many people are unhappy with Nissan and the way their complaints are not heard. Consumer affairs instructed me to take my car to Nissan dealer and have a reading done to see what problem code would show up on their meter. The cost would be one hundred twenty dollars with no guarantee that Nissan would replace converter. I gave Nissan enough of my money so I'll just have to find a reputable repair shop and get estimate before work is done. Stay away from Nissan dealer as much as you can. I am in market for a new car soon and it sure won't be a Nissan.