So, my SES light came on yesterday and it read P0420 (catalyst system running below threshold Bank1). I had this same error about a year ago and the dealer said it was the infamous exhaust bracket issue and fixed it. The light has not been on since. It just came back on conveniently right at about 81,000 miles.

I know there are a lot of threads on this issue, but I am not really savy on the specifics (ie. headers, pre/post cats) all of that. I guess my question is, what are the chances of this being an O2 sensor and me getting it fixed for less than $250?

It is at a garage right now that said they could look at it, but I am not too confident that I won't have to take it to the dealership.

I guess I am just looking for some advise from some of you that know way more than I do about this stuff. What should I be expecting here?

Thanks in advance, you all are always helpful!

 

broken pre cat and expensive fix...I hope Im wrong and its another heat shield issue.

 

Ok, that is not too good. Got that on my wifey's 04 Camry now with 140k miles. Dealership says its the catalytic converter and that it is a $1200 job. Well, it is not a Maxima, but since it is the same code, I thought to share. Well, as for my wifey, we have been looking at the 08+ M35. So, we decided not to fix it. Will just be looking for her new ride until we hopefully buy it.

So, I am guessing same with your car: Catalytic converter needs to be replaced. Remember, I said, my guess. As for my wifey's own, it is dealership diagnostic on her Camry.

I wonder what can go wrong to keep on driving a car with that light on. And for a whole year. Anybody can share some light on that question? What is the worst that can happen or go wrong again with the light on?

 

By my used ones alot cheaper and in good condition..

 

Thanks for the responses. Vigilante, I sent you a PM about the heat shield, I have never heard anything about that before, sounds interesting.

Gianniali, I was told to go OEM for cats and O2 sensors because the cpu might not recognize that they are funtioning properly if they are not specifically made by Nissan. Is this true, or bs in your opinion?

Thanks again,

 

The pre cats can tend to crumble and get sucked back up into the manifold, which is bad. If the heat shield on the exhaust is broken (the welds are terrible and will open the ehaust up giving a leak) which could set off the O2 sensor and SES light, however most of the time the pre cat will be bad as your car has 81K on it. if you have a good relationship with your dealer, they may fix it on good faith as you are right past the 80K mark. Good luck.

 

As far as I know it is true, with experience that many have had with putting on headers and trying to simulate the correct and equal air flow from one sensor to another, hence then recieving the Check Engine Light..... The headers with Cats that I have are OEM