My max threw the subject code and all I can find is reference to the code being HO2S bank 1 sensor 3.

Does the 03 SE even have a 3rd sensor in bank 1? If yes, then where is it and how do I trouble shoot it?

There is no sensor 3 on your car. P0042 is one of the codes in the standardized OBD code set. While an auto manufacturer does not have to use it, it is possible to show up.

How did you "discover" this code? Do you have your own code reader or did you go to an auto parts store? Either way, I would get the code re-read and see if it really is P0042. If it is P0042, I would reset the code and see what comes back.

Thank you. That is what I was figuring. The cel came on last night and I did the self diagnostic pedal tap procedure to retrieve the P0042 at the gas station. I have video of the cel blinking and can try post here if you want me to.

I deleted the code last night. By foot and hand.

Something is wrong either with the readout or your counting, the ECU is not going to display a code that the ECU doesnt know exists. Please post the video, seems more likely that it was a P0420-Three way catalyst function

I bet that I am reading it wrong and the code is like you suggested, P0420, I am trying to upload the video but it may take me a few hours as I am replacing the front motor mount and endlinks plus my dog is at vet getting sutures and I may have to go get him at spur of moment.

What is treatment for a P0420 code? I get the video posted hopefully tonight but it may be tomorrow a.m.

Thank you for the quick responses and all of your help thus far.

So I got the P0420 this morning and have been looking here for the fix and it is not exactly clear what I should do:
1. Replace catalytic converter?
2. Install aftermarket headers?
3. Install aftermarket y?
4. Replace o2 sensor?

Any other ideas besides taking car for ecm update or flash, etc.?

start cheap and work your way to expensive. O2 sensor would be my first stop, then the cat. Y-pipe and headers are alternatives to replacing a bad pre-cat and require also installing an O2 simulator, which would get rid of the code whether you remove the cat or not. IF your precat is bad you will want to either replace or remove it, letting a bad cat remain on the car can be detrimental to engine life

How many miles on your car?

212k

Do you have any suggestions for how I can search for these parts? Part numbers?

212k, yeah your precat(s) are probably toast by now. Not sure what part numbers you would be looking for. Since there is no O2 code you dont really know which pre-cat is the problem and they are $$$$$$$ to replace so just buying a replacement and hoping its the right one doesnt really work great.

That's kinda what I was thinking as well. So, can I do something else besides replace o2 or replace precat? Buy sims and install headers or y?

Really don't want to try the seafoam method. Nothing against seafoam just looking for a more permanent solution.

sims will work to get rid of the light, but not the problem. Gutting both precats and installing a sim will get rid of the light and the problem.

It is also possible for a bad sensor to throw the P0420 code and not have a bad precat or throw an O2 sensor code, but that is unlikely and at 212k miles its unlikely that either precat is much good

Thank you for the advise.

I am still curious about how some have removed their precats and what they did to replace the factory setup. Gutting my precats is definitely a practical solution for me. I have seen some info on a "ghetto sim" but I am not sure if it is applicable here or not. I have also inquired about the o2 sim product and contacted the company, but awaiting their reply.

Again, thanks for the quick responses.

Here are a couple of threads with some useful info on replacement.

I'd go with headers personally.

But, there are other options.

http://forums.maxima.org/5th-generat...ighlight=bosal

http://forums.maxima.org/5th-generat...ighlight=bosal

P0420 is the bank 1 pre-cat. Bank 1 is the firewall side.

P0430 is the bank 2 pre-cat. Bank 2 is the radiator side.

I would suggest you get a warpspeed y-pipe and gut the bank 2 cat. You will probably have to get an extender for the O2 sensor.

Ok. Let me think about this a little longer. Thank you! The details are where I'm hung up.

Headers have been difficult for me to locate for some reason.

Would these work?

http://www.rsaperformance.com/obxexhesy02n.html

If yes, then do you all know what I would need to do to make all o2 sensors accounted for?

Threw both 420 & 430 codes today. Replaced bank 1 o2 sensor.

I have found a lot of information on here on the 01 maxima with this problem but I have an 03. Not sure if that makes a whole lot of difference but looks like some 01s were 3 o2's only and from 01 to 03 cali spec was mandated.

I want to make a change and try to get rid of this problem but don't know if I can avoid gutting at least 1 cat because I can't find headers to purchase.

Just wanted to keep the org posted.

Best regs,
-A

As an aside I fixed my hot start problem by cleaning my downstream part of throttle body.

Yes, those will work, as will these, albeit slightly overpriced.

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

I can't find any company that doesn't have an 8 week lead time. That might explain the pricing here.

Who have you called?

I found some but I wanted obx. Obx is out of production...

I found some Megan headers for 225 plus shipping.

I was going to gut my precats but got all into it and removed the front precat only to find that my downstream o2 didn't want ti come out. And since I didn't want to risk messing up the nut I just decided to wait 4 days and bought the Megans and reassembled.

I guess I will have to heat up that o2 to remove it over thanksgiving holiday. I plan on using the nonfouler spacer method when I install the headers.