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Discussion Starter #1
Hey guys. I have an 04 SE Murano with almost 228k on the cluster. I currently live in Cali and need to get my smog test done asap, so I can register the car in less than 3 weeks. Anyways, I get the occasional Check Engine Light due to a P0420 code. That code comes and goes...and so does the light.



As of today, the CEL is off. I did have the codes checked, and since the light is off, the P0420 is not showing up anymore. On the other hand, the P0302 is popping up on the scanner, even without the CEL. From my understanding, it is a cylinder 2 misfire (the "02" in the P0302 meaning that it's cylinder two), which will fail me during the test. Without digging in too deep (since I don't have much time, or work space, or any real sense in spending much money on a car with these many miles), would anyone know if replacing the #2 cylinder coil possibly fix the issue?


I did replace my spark plugs with the OEM set about 50k miles ago and don't believe they should be causing an issue. The #2 coil should be right upfront...resulting in easier access than having to remove the entire intake mani, like I did to replace the spark plugs (maybe I could swap between another coil up front). Truthfully, I do not want to spend much time, money and effort on this car. Im ready to replace the beast but would like to run it until I find my next vehicle. Any help would be great. Thanks in advance!
 

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Discussion Starter #3
Yeah that's what I was thinking, switching with cylinder #4 coil. I may do that tomorrow and have codes checked again. Problem is I got this little cheap scanner that is said to work well... Unfortunately, I can't seem to get it to pull anything up properly. I may need to take it to get codes pulled at a shop once I do this.
 

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AZ / O'Reilly will do it for free. Swap it in their parking lot. Any code that comes up should make your CEL light up. Cannot erase the code and go get a smog. You will fail. Car computer needs to have so many cycles to catch up before getting a smog check.

I have used the anti fouler trick on my 99 [email protected] 420 code and has never appeared again since. Smog 2 -3X already. We have annual smog check here in NV. But way more lenient unlike CA. They have not check the underside either. If they do, they will see the anti fouler if they know what they are looking at. Works great.
 

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Discussion Starter #5
Well that's the problem. Autozone does not check for codes in Cali (yeah I was surprised myself when I moved here). I believe Pepboys still does it. I will swap the coils today and get that checked out. If the coil is the issue, I will replace that from one I can find in eBay. Afterwards, I'm not sure if I should just have them erased at that point and drive the few cycles, or if I should just drive the car until it clears itself? I'm not sure if the code will stay in there long term even when the issue is fixed?
 

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A code reader is not expensive, and saves you money the second time you use it. Readily available at any auto parts store.

We had some trouble getting the drive cycle idiocy right on my wife's 2009 BMW 328 - I found specific directions online about the precise speeds and times to drive at each speed, and it still took repeated attempts and a week of normal driving to get the cycle right. Most screwed-up thing I've run into on a car yet.
 

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I think CA AZ will lend you the code reader for free while you step out to their parking lot and use it in your car. They just don't do it for you. You then go back to the store and they print out the reading. Even better. You can erase the code yourself I guess. Here, they are not allowed to erase codes.

If the coil pack is the real problem, after replacement and erasing the code(clearing the CEL), drive for about 100 miles for several days or so, and if the CEL does not comes back then you are good to go for a smog.
 

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Discussion Starter #8
Thanks guys. I'll go swap the coils this evening and get the codes checked out somewhere. I will also throw in a bottle of seafoam and 93 octane to keep that CEL off. Seems like that helped the several times that I tried it. I guess I can use that as extra insurance so that the P0420 doesn't trigger the light. As I mentioned, the light is currently off and the P0420 is not showing up either. Seems like only the P0420 code triggers the CEL...and not the code for the misfire itself.
 

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Discussion Starter #10
So here is an update: I went ahead and moved #2 coil to #4 cylinder last evening. I used my little scanner and it was popping up as NO CODES during that time (I assume I checked it properly yesterday, since I had trouble reading the codes in the past...I assume that it was maybe user error).

Anyways, my CEL came back up today. I went ahead and used my scanner again and figured out how to get the codes to pop up. I did get codes: FAULT: 2, PEND: 1....I have the P0420 and the P0302 popping up again. Then another P0420 with the letter "P" after it....I assume that means "Pending" for whatever reason?

Since I switched the coils around, I assume and HOPE that it is only a faulty spark plug in cylinder #2 . What I may do today is keep the coils in the same spot they are in but move the spark plug from cylinder #2 to #4 and see if that causes a new issue in cylinder #4 . It does not appear that the coil was at fault.....at least not from my readings today.
 

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Discussion Starter #11
The current spark plugs were replaced about 50K miles ago with the same factory NGK, so they should be good. In addition, while looking down at the spark plug after removing the coil in #2 , everything was clean and dry. No oil or coolant were present, so it still appears to be a cylinder #2 issue of some sort. I'm worried about this more because the P0420 comes and goes, and when it goes, there is no reading for it. Seems to go away with better gas and some octane booster and/or fuel cleaner like Techron.
 

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Its possible that the 302 is being tripped by the 420. I would eliminate the 420 code first by attaching the anti fouler on your O2 sensor bank 1. For <5 bucks its a great fix. Then, see if your 302/304 code comes back. If it does, and it followed the coil pack from 2-4, then you know which one to change. Cheapest way to do it I think.

Look here...http://www.nissanforums.com/pathfinder/160693-code-p0430-change-one-both-os.html

And here....http://nissanhelp.com/diy/murano/projects/2003_2007_nissan_murano_air_fuel_o2_sensor_location.php
 

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Discussion Starter #14
Yesterday, I swapped both the spark plug and coil between #2 & #4 cylinders. Went to autozone and they let me use their scanner. Both the codes came up again (same codes) but I believe they haven't really truly reset themselves at that point.

Today, my CEL went away, so I assume that it has all reset on its own. Anything that pops back up at this point should be more up to date. I assume it may now be the regular P0420 and possibly a P0304 (since I moved the coil and plug over)....I guess I have to wait and see. Worst case scenario I add a new coil, dump 93 octane and some seafoam in the tank, and hope it passes that way. I still have to wait and check the codes that come up when they do. Again, if it is a misfire issue, it should pop up an issue in the 4th cylinder now. Once again, I don't believe the 50k mile plug to be an issue...I would think it's the coil if anything.

The CEL is off but I should stop by the autozone and see if the other misfire code comes up regardless (as it did at the smog shop earlier this week when the CEL was off). My little scanner says NO CODES, when I just checked for them...but I'm not sure if I trust the cheap thing.
 

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If it has reset, a good approach is to take it for a good long drive and let it get happy withitself.

When you go for the smog check, make very sure it's FULLY warmed up. Those systems work best and are cleanest when they're good and hot.
 

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Discussion Starter #16
Yes, it is still reset today...no CEL. Also, today I went to autozone and nothing new is popping up on their scanner (although my old codes were in their system on the computer..I guess associated to my VIN?).

Anyways, I went ahead and put in 91 octane (Cali premium) and put in a full bottle of the Techron complete fuel system cleaner and some seafoam (this has kept the CEL off for a while in the past).

Also, I may have to agree with deeman on the P0302 following and tripping when the P0420 is present. I say this because if the coil or plug were a big issue, it should be popping up in the #4 cylinder now...unless I need to give it some more time.

Anyways, I'll keep driving it tomorrow. If it doesn't pop back up, I may pull into a SMOG testing station and get the test done. I should have about 100 miles on the car since it turned off...but we'll see what happens by tomorrow afternoon.
 

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Discussion Starter #17
PASSED. Decided to go to a local smog place and explained to the guy what my situation has been. He did a pre-test and said that it should pass. I believe he was a lot more laid back on the test than the first place I had it done two years ago, when I first moved to California...as far as the physical inspection goes.

Seems like the higher octane and some fuel cleaner/seafoam does the trick for the P0420 code. The P0302 is still a mystery. The guy told me that if the code doesn't get triggered again and includes cylinder #4 for the misfire, then it could still also be a cylinder #2 injector issue. Again, I do believe that it may just be a random code being triggered whenever the actual P0420 comes one...

...but I'll check for codes again once the CEL does turn back on. I'm still curious to see if cylinder #4 pulls anything up.
 

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Discussion Starter #18
Its possible that the 302 is being tripped by the 420. I would eliminate the 420 code first by attaching the anti fouler on your O2 sensor bank 1. For <5 bucks its a great fix. Then, see if your 302/304 code comes back. If it does, and it followed the coil pack from 2-4, then you know which one to change. Cheapest way to do it I think.

Look here...Code p0430:change one or both OS sensors - Nissan Forum

And here....2003-2007 Nissan Murano Air/Fuel Ratio and O2 Sensor Location | Nissanhelp.com
Although everything is running okay with my vehicle today, and I did pass the smog test in June, I would like to add the anti-fouler to my car because I am still constantly running the P0420 code. Could someone explain which exact O2 sensor I have to tackle to add this anti-fouler? I would like to get this done today if possible. I did see it saying "Bank 1"...but is that sensor 1 or 2? What's my best way to approach it from outside of the vehicle? Is it from under the hood or under the car?

The CEL and horrible gas mileage is something that I'd like to fix for sure. Any help would be greatly appreciated. Thank you.
 
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