mazda626es

iTrader: (1)

My girlfriend has a 2003 Maxima with 126,000 miles on it and her SES/CEL light has been on for a a few weeks now, but has been turning On and Off for the last 6 or 7 months (right after I replaced the radiator), but every time I would be driving to autozone to get the code pulled, it would shut off. So a last week, my girlfriend brought the car to the family mechanic (i'm pretty good with most car related things, but by no means am I a mechanic), and the guy said that car had a bunch of codes that were on(didn't give me a list of specific codes), but he said that at the end of the day, it was the bank 1 catalytic converter. Now, they have been going to this guy for over a decade, and I've met him a few times and he seems like a good guy/mechanic, so, for the most part, I can trust him. But he said that to replace the bank 1 cat, he was going to charge a $963, which seemed very high to me. So I called him and he said that on Nissans and Toyotas, he only uses catalytic converters directly from the manufacturer and nothing aftermarket, but that since he knew us, he would put in a cat that we provided (amazon.com has a Walker or Bosal bank 1 cat for $210 versus between 500 and 800 directly from nissan). But since we are talking about so much money(I am aware of the trick where you take out the o2 sensor and put in a different type of plug, it will make the light shut off, but I want to fix it right.) So I told him not to do the cat, that I wanted to price some things out first and maybe try and do it myself. So tonight, I bring the car to autozone to get the codes pulled, thinking that it will only be the P0420 code. But when I get there, I get the following codes:

P0420 - Catalyst System Efficiency Below Threshold (Bank 1
P0455 - EVAP Control System Gross Leak
P0456 - EVAP Emission Control System Very Small Leak (Negative Pressure Check)

Now at this point I get home and start doing some research and I come across this article:

http://www.easterncatalytic.com/educ...he-po42o-code/

Which now makes me think that there is a vacuum leak, or maybe a faulty vent control valve that is causing the P0420 code and the cat is fine.

Now, I'm in a little bit of luck. Because I too, have a 2003 Maxima (not anywhere near as loaded up as my girlfriends, but I like it just the same) and I also have a 2002 Maxima with a blown motor which I'm in the middle of trying to part out. So I do have access to plenty of parts/hoses and such. My question is, can anyone tell me how to proceed? I was thinking of switching out the vent control valve and the canister with the one on my car(I know its good) and then maybe going somewhere to have a smoke test done to see if there is any leaks. But with these 3 codes at the same time, I'm very torn about how to begin. I will also mention that the gas cap on the car is only a year or so old, and most of the time, she only uses 93 octane gas. Any suggestions I can get from you guys would be extremely helpful, and sorry for typing the book, I just wanted to get as much information in as possible.

DennisMik

iTrader: (2)

You are thinking logically and that is good. The link you posted is saying that when you flip the switch to turn on the light in your house and the light doesn't go on, the light bulb is not the only possible cause. This is true in almost everything that might fail. It may not be the obvious.

But I'm pretty sure that the P0455 and P0456 are not causing the P0420. If you read the FSM for P0420, it says to check half a dozen other things besides the cat. The EVAP system is not one one them. Many people have had the P0455/456 codes and did not have the P0420/430 code.

See page 331 - http://boredmder.com/FSMs/Nissan/Maxima/2003/EC.pdf

As for the P0455/456 codes, the list of possibilities is a lot longer. See page 390 in the link above. Since you have the ability to swap parts, go ahead and swap the EVAP canister and the valve on it. Also swap the gas cap. Just because it is fairly new is not a guarantee that it didn't go bad or that the o-ring on it didn't get damaged.

nestorlugo

iTrader: (11)

Op....i nevere had the other codes but i did experience the 420 for a while at the beginning....along with some misfire ones ..... make certain you and your gf dont skimp and use cheap gas,because when i first took ownership of mine i would neglect my car with cheaper gas not knowing the ugly... even now with 93 octane i get the bees in a can chatter in the hot days but in the cool days its little to none existing.

mazda626es

iTrader: (1)

Thank you for the FSM, i've been looking for that for ages and I used to have it on my computer, but I have no idea where it went. I think I may try the spark plugs first. I know they are a huge pain in the *** to do, but the car has 126k on it and hasn't had the spark plugs done yet. The car starts up a little rough so I think it maybe time for that to get done on it. I'll also try switching out the valve, canister, gas cap and PCV. I also tried this stuff that autozone had, called CataClean. I talked to two people at two different stores and they said it works phenomenally well.

mazda626es

iTrader: (1)

Ya, I have gotten that bees in a can chatter on every maxima I've owned. I've seen a TSB out from Nissan for a VTC(?) replacement, but from reading about it, replacing it is more trouble than its worth. She does use cheap gas every once in a while but I've been making sure for the last few weeks(since the CEL has been on), she has been using 93 only. I read another article about this as well:

https://www.discountconverter.com/ca...rter-&News=120

And I keep seeing that the car running lean can cause the P0420 code to pop up. Unfortunately I do not have a ODBII sensor, so I can't see what the car is doing. Although, after this, I may just go out and buy one because it'd be nice to see what the car is specifically doing. But for now, I think I'm going to start off replacing the PCV valve, cannister, vent valve, gas cap, and front 3 spark plugs and see if I can find and leaks in the exhaust or the vacuum lines.

mazda626es

iTrader: (1)

And its not that I don't appreciate the help, or that I don't think its the cat, I just want to be sure before I go dropping at minimum 200 bucks on a part I may or may not need. Not to mention the hour or two it will take me to replace the cat. She needs the plugs anyway because the car is running a little rough and her MPG isn't what it should be, shes getting on average 21.8 mpg. I just think that its very (even too) coincidental that there are 3 codes, even after clearing them out and driving around. I don't know, my gut tells me its not the cat and its something else. What that something else is, I'm not 100 percent sure yet. But i've learned over the years to listen to my gut, after all, it is quite large, lol.

mazda626es

iTrader: (1)

Also, thank you. I try and use logic as much as possible. Its helps me narrow down the list of problems and or figure out what a specific problem is. But I also try and listen to my gut a bit as well. I can't tell you how many times I have ignored my gut feeling because of what someone said or something I read, and it would up biting me in the butt.

mazda626es

iTrader: (1)

I changed the front 3 plugs, pcv valve, and the car now has a new code, it still has the P0420 and P0455, but not instead of the P0456, it has the P1456 code. I am extraordinarily lost.

Itz Shak

Good luck, I've also got a catalyst effiecency po430. Just gotta replace those parts bro, let us know how it goes.

ManualMaxima

iTrader: (10)

In case you do end up getting another cat, I installed a BOSAL unit (instead of oem) some time ago, no problems, happy with the purchase...

DennisMik

iTrader: (2)

The P0456 and the P01456 are pretty much the same, if not identical, code. Both those codes are EVAP system small leak. Code P1456 is on page 573 in the link I posted earlier. If you compare page 402 (P0456) and page 573, they look identical to me.

I guess that you being confused is exactly what Nissan wanted. Mission accomplished.

mazda626es

iTrader: (1)

Lol, well then they got what they wanted. This weekend, im going to try a few more things. Back plugs as well as putting on a new vent control valve, gas cap and manually checking for leaks before i pay 90 bucks for a smoke test. I also might swap out the down 02 sensor with the one off my car and see if the codes follow, but now im just thinking the cat needs to be replaced. God damn my gut.

And a bosal cat huh? Did you do it yourself? If so, was it hard to do?

mazda626es

iTrader: (1)

Well, after I did all that work the other day to her car, the light is still off and she's driven about 150 miles. I got a scanner, so I'm going to be running some tests tomorrow to see if there are any codes pending, but so far so good. Now I just have to do the rear plugs on her car and she should be all set. I did the plugs on my car. Wound up having to do the rear valve cover and rear valve cover gasket as well. Ugh, what a pain in the ***.

dwapenyi

iTrader: (3)

At 126,000 miles:
you were 26,000 miles overdue for a spark plug change. Get all 6 changed.
Change the primary O2s if they have never been changed before. They are tired.
Leave the secondary O2s as is
I doubt that your catalyst is finished.....maybe at 200K miles but not at 126K.
Change the PCV valve too

After doing the steps above see if the CEL goes away for good.....if not, then change the cat.

Also, a known cancerous sickness of quite a few 2002-03 Maximas is the pre-cats disintegration issue that could ruin your engine. Look at this guy going through some serious denial issues;

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

For extra credit i suggest finding a shop to gut the pre-cats in your maximas

mazda626es

iTrader: (1)

I keep reading about that problem. I just did all 6 plugs, pcv valve, and replaced a few of the coils. The car has a P1456 code on it now, but no P0420 anymore. Should I just redo the cats? We've had the car since it had 60k on it and have done all/most of the maintenance to it. I don't think the cats are gone yet. However, I would rather replace the cat(s) for a few hundred bucks than have to replace the engine. What are some of the signs that the cat is destroying the engine? And which cat should I replace so the engine doesn't get destroyed?

dwapenyi

iTrader: (3)

Replace both (2) pre cats, then change your oil and filter. Ideally I would get an aftermarket Y-pipe like warpspeed which deletes them by default. To see whats going on, download your FSM from here;

http://boredmder.com/FSMs/Nissan/Maxima/2003/

Open up the EM.pdf document. Goto EM page 10. The pre-cats are the ones labelled 3 and 7 in the diagram.

mazda626es

iTrader: (1)

The one bank 1 cat looks like its a lot of fun to do. The one by the radiator, i'd imagine, I could just unhook the fans and radiator if I had to and have more room, the one in the back by the firewall, that looks like a PITA. I opened up another thread on the subject of cats, now that I think I have this problem worked out. I can get either a bosal setup, or walker setup for just about the same amount of money. (both cats and the y pipe).

dwapenyi

iTrader: (3)

If you are DIYing search for a 5th gen Y-pipe or headers install. There should be a bunch with PICs.