So I've owned my Maxima for about a year now, and ever since day one, I've had the P0420 code. The hasn't driven badly except for a little hesitation around 2800 RPMs until the engine gets to normal running temp. But just last night, I went to start my car, and my SES light goes out, so the first thing I thought was, the light burnt out. So when I went to start the car this morning, I noticed that the SES light is lite up, and once the engine turns over, the light goes away.

Is this weird that my SES light just decided to shut itself off?

 

um...

The SES light turning off shortly after engine start is called NORMAL.




You're so used to having it on that you don't know when it's behaving like its supposed to. The code you had likely went away TEMPORARILY...

 

If it was a P0420 code then yes...it went away, but temporarily as Amerikaner mentioned. It will be back...it always comes back at some point.

 

Do I have to replace the main CAT to get this code to never come back? Because I bought a Y pipe when I had the P0430 code, and I havent installed it yet. But everyone has been telling me that since I have Cali emissions, than the Y pipe won't fix my P0420 code.

 

The main cat won't do anything for the SES code. P0420 code is for bank 1 which is the firewall side where you would install your y-pipe to replace your pre-cat.

Our Maxima's have three cat converters (two pre-cat and one main cat). The P0420 is bank 1 pre-cat and P-0430 is bank 2 pre-cat.

I don't know if installing a y-pipe will take care of the code, but I would suggest since you have the y-pipe already you install with a NEW bosch or OEM front bank 2 O2 sensor. Then make sure you clear the code by an ECU reset or scanner clearing.

Then wait and see what happens...if the code comes back then you are going to have to take others steps. What kind of emissions requirements do you have in NH? Is it a visual inspection, or does it include a sniffer test on a dyno?

 

The y-pipe will eliminate the bank 1 pre-cat(your p0420 will not go away unless you get an O2 sim). You will still need to do something about bank 2 because 1999-2001 cali spec maxima's y-pipe doesn't eliminate bank 2 precat. If you don't want to go that route you can always just buy a aftermarket pre-cat and be done with it.

 

So I should just buy an aftermarket pre-cat instead of installing the Y pipe?

Then wait and see what happens...if the code comes back then you are going to have to take others steps. What kind of emissions requirements do you have in NH? Is it a visual inspection, or does it include a sniffer test on a dyno? They just do a visual inspection here in NH, they do not use the sniffer test that you have in CA.

I didn't know how to quote two people in the same post.

 

Hold on...one thing at a time here. You only have the P0420 code to deal with. I was providing information on both pre-cat codes. Deal with the one issue you have for now.

Since you don't have a sniffer test go ahead and install your y-pipe with a new O2 sensor. There is a chance this will take care of your P0420 code. If it doesn't then you can go the O2 sim route BigLou mentioned.

Since there is no sniffer test don't bother getting an aftermarket pre-cat as it will only cost you more money, not last that long, and you'll be back to square 1 before you know it.

To quote two different people you reply to one person, then copy everything, cancel the reply, then reply to the second person with quotes and paste your initial quoted reply from the first person.

 

the easier way to quote more than one person is to hit the little button immediately to the right of where it says QUOTE...this is the multi-quote button. Click that button on each post you want to respond to, and then click on "post reply".

the above does NOT work on mobile though.

 

Okay, I will install the Y pipe and install a new Bosch O2 sensor along with it. But shouldn't I repalce all four O2 sensors when I do this?

 

Thank you for letting me know how to do this. Although, I am using my phone most of the time, so I'll probably have to go the route of what Foodmanry was talking about.

 

Nope...only need to replace the front sensor on bank 1.

 

That is the sensor I can see sticking out of the exhaust manifold when I pop the hood right?

 

Nope, the O2 you see when you pop the hood is bank 2(closest to radiator).

http://forums.maxima.org/5th-generat...-question.html

the diagram in post #2 shows you the 4 locations for the O2 Sensors on your car(It would cost a lot to replace all 4 when its not necessary).

 

Yeah because there about $100 bucks a piece right? So yeah, I don't want to replace O2 sensors that I don't need to. I'll see if I can find that O2 sensor that's at bank one. This might be a next week project since I don't know how long it's gonna take me to get the stock Y pipe off. Someone on here told me that I'm gonna need a torch because Nissan welds the stock exhaust bolts on and they would be impossible to loosen without doing so.

 

The someone that told you they weld them on is an idiot. They can be difficult to get off depending on the level of rust on them. I would recommend PB blaster and waiting 30 minutes then have a go at them with a breaker bar. You'll need a myriad of extensions and attachments to get the socket in there, but it can be done.

Last time I replaced my y-pipe it took me about 45 minutes. But...I live in Southern Cali where we have no rust.

FYI...you have to jack up the car pretty high to have room to pull the stock y-pipe off. I had to put my jack stands on some concrete blocks to give me enough room.

 

Damn, I guess it's a good thing I asked this question again. Also I had no idea that I needed that much ground clearance to get the old Y pipe off. I might just take it to a muffler shop and see if they will install it for a reasonable price.

 

A muffler shop has good labor prices...not a bad idea. They'll probably install it under a $100 and be done with it in 30 minutes.

 

Yeah that's probably my best bet. Then I don't have to bust my *** trying to get a bunch of extensions on a wratchet to take out the exhaust bolts. Thanks again for all your help.

 

Yup...no problem. Oh..FYI, get new exhaust gaskets before you have the y-pipe installed. You'll thank me later...

 

Thankfully the Y pipe from Warpspeed came with all new gaskets and bolts.

 

P0420 is catalyst efficiency and could be pre cat or main, I know all of you say it has to be pre but its not always the case. I have a fed spec and had p0420 and bought the ypipe and pulled stock one off and pre cats were fine and main one was all messed up. May be different since you have California spec and o2 sensor is before main cat. Main cat is also bank one. Good luck

 

The P0420 code is for the pre-cat. The downstream o2 sensor for the main cat will not throw a code. The sensor that throws that code is way upstream of the main cat. There is no way a main cat would cause a P0420

 

I can see how that might be the case on a California spec because there is a O 2 sensor after the pre cats. on a federal spec car there are only 02 sensors before the pre cats and after the main cat so how can there be a code for a pre cat when there are no sensors measuring efficiency on them? Logical? like I said mine had to 0420 code and it was my main cat that was clogged up I cleaned it out and low and behold I still have a P0420 and my pre cats were fine before I replace them with the ypipe.

 

OP has Cali spec.

 

Yes, my car is a Cali spec. I'm starting to feel like most Maximas are Fed.

 

Most newer Maximas are cali spec. The fed spec was last used in 2001 I believe...or perhaps in the 2000 model. Anything 2k2 and newer is Cali spec.

 

I did not know this.