# 2001 Pathfinder 3.5 LE - P0420 Code - Found much info, have a few questions



## jvaruzzo (Aug 23, 2003)

I looked through all the previous threads on this forum regarding P0420 and the catalyst system.

My particular problem was a loss of power for about 10 seconds, not complete loss, but very rough, during the loss the service light was blinking.

Everything was fine after that (4WD active, in snow, very cold 15 F degrees).

The light did NOT remain on.. it turned off immediately when normal operating conditions resumed. However, a few days later I did plug in my code reader and saw the stored "P0420".

I've read about the ECM updates with the TSB, and front or rear catalytic converter replacements. 

The major questions I have, all the threads mentioned the light and code, but no one mentioned if they experienced any engine issues prior/during with the light?

Does this scenario change anything? I read one other post on a different forum that mentioned a bad ignition coil. 

Lastly, a few weeks ago at about 85,000 miles the SES light came on twice, both times my code reader just said "CHECK SERVICE BOOKS"? It didn't have any P code. I cleared it. The light came back on a day later, but my reader said "No active codes" - the "CHECK SERVICE BOOKS" code was stored. This was not accompanied by any problems. I reset the light again and it has been a couple weeks with no problems until now.

I apologize for the lengthy post, but I wanted to be thorough, and hopefully fill in the blanks for anyone else who has this problem in the future.

Any help, as always, is greatly appreciated.

Thanks,
Justin


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## mpe235 (Jan 19, 2009)

Sounds like your code reader is not capable of displaying the stored code. You will want to try another code reader. The blinking ses light usually indicates a misfire. The 3.5L pathfinder engine has been known to lose screws from the power valve and have them fall into the cylinders. When they do they usually hit the spark plug and close the gap so the plug does not fire. They can also cause internal damage. It is pretty easy to check the screws. Remove the upper portion of the intake manifold and you can see the power valve and screws.


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## jvaruzzo (Aug 23, 2003)

Wouldn't a screw bouncing around in a cylinder make a big mess real fast?

And why would this cause the P0420 code?


Sorry I'm not at all familiar with the pathfinder engine ...


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## mpe235 (Jan 19, 2009)

jvaruzzo said:


> Wouldn't a screw bouncing around in a cylinder make a big mess real fast?


Yes.



jvaruzzo said:


> And why would this cause the P0420 code?


Because the misfire causes excessive unburned fuel to pass through the engine into the exhaust where it is then burned by the cataytic converter thus damaging the catalyst material.


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## jvaruzzo (Aug 23, 2003)

Is it worth putting in new plugs and wires first? Couldn't that lead to a misfire?
I'd rather knock out any easier regulat maintenanve items before tearing half the engine apart.

And could a coil still be a possibility?

Thanks
Justin


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## Richid (Oct 27, 2007)

Hi,

I had the same problem with my 01. I used to get a real rough idle / hard start and it would set a catalyst code. Now, I like my PF but not to the tune of new cats. So I just left it alone and reset before inspections. 

About two months ago I started getting a misfire code, but it would not pinpoint the cylinder. Two weeks later the bad coil finally failed - these were the replacement coils, about 5 years old, but the new part #s.

Hope that helps,

-Rich


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## jvaruzzo (Aug 23, 2003)

Thanks for the update, so I'm now armed with the following:

Misfires (during momentary loss of power) likely threw the Cat code.

Misfire could be caused by power valve screws in the cylinder or a bad coil.

Can anyone confirm or deny if they had engine performance troubles with the P0420 error, that was corrected by the ECM update? Or the ECM update simply fixes a bug with the SES Light itself (no real problems, just a software issue)?

I'm assuming ECM is just for the light, and never experiences actual rough idle or loss of power.

Finally - where do I start? How do you diagnose a coil or a screw in the cylinder, or could even be bad gas for all I know! More importantly, what do you check first?

Is there any preferred checklist of parts or items to check that lead to the blinking SES and loss of power? My code reader does show live data, is there anything I shoudl be looking for there to help diagnose?

Thanks,
Justin


Perhaps for now I'll let it go and see if it happens again anytime soon.


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## Richid (Oct 27, 2007)

Hi Justin,

My local dealer swore up and down that there was no update available for my ECU, however after they performed the gas fill recall, I have gotten a code - except for the bad coil. If you can find a good dealer, they can put on the Nissan Consult system and pinpoint the exact problem - but don't be surprised if they recommend new cats. I just waited on mine - it only ran crappy for a few seconds before clearing itself up. I lived with that on and off for about 6 months before the coil was bad enough to throw a code.

Hope that helps...

-Rich


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## jvaruzzo (Aug 23, 2003)

*P1320 Code*

Ok, now the SES light came on again, this time it came up with code P1320 - Ignition Failure.

I quick check seems to point to a bad ignition coil, which would support the misfire, which would explain the catalytic code and stammering that was experienced.

I read a few places that all 6 ignition coils should be replaced at once, they seem to run a little under $100/piece... Is it really nescessary? Is there anyway for an average DIY'er to test an ignition coil that is on its way out?

Thanks,
Justin


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## Richid (Oct 27, 2007)

I'm no expert - I had also read that all of the coils should be replaced at the same time. My friend, who is a mechanic, recommends this - but that is only because they kept getting complaints about the other coils failing after a single repair. I believe that dealers also recommend this course for the same reason. Another posting (maybe even on another board) mentioned that the new version of the coils have a small black dot - which is just a sticker, on the new versions of the coils. I noticed them on mine when I replaced the bad one.

My pf has over 100k miles now, so I only replace what is broken...


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## eschot (Mar 6, 2010)

*2001 Pathfinder P1320, 0300 blinking SES*

The 1320 code was accompanied by an 0300 code and a blinking SES on my Pathfinder. The problem was intermittent and I soon realized that I had a faulty ignition coil as both codes were related. The 0300 code wouldn't specify which coil was faulty and I have 109K on the car. Needless to say I didn't want to fork over $70 - $80 x6 to replace them all let alone even have the dealer do it. So, I hooked up the diagnostic tool again that I borrowed for free from Autozone and cleared out my codes. After that, I ran the truck again with the tool still on and drove until the SES blinked again. My persistence paid off as I got a 0305 code -- meaning it was the 5th cylinder that had the misfire. 

Replacing the coil and spark plug was fairly easy and took me roughly 45 minutes (my first time doing this). A Haynes manual will explain in detail. I cleared out the codes again -- this time the light was off for good and the engine was running better than ever. If you have a little time and patience you don't have to replace all the coils at once and you will save a ton of money especially compared to having the dealer do this.


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