P0420 Code solutions

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billdurham
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Joined: Sun Sep 12, 2010 4:02 pm

P0420 Code solutions

Postby billdurham » Sat May 09, 2020 8:45 pm

Guys,
I have a 2005 Pathfinder SE 4X4.. its relatively low mileage.. about 114k. I bought it in 2008 and its been a great car. Anymore, I don't drive it that much.. just to tow my boat to the lake or run to Home Depot. Sitting is the absolute worst thing to do to a car and things are creeping up now because of it. It developed a miss recently.. would randomly run on 5, then run perfect. It popped a code for the cylinder miss and after a couple of cans of Seafoam and just drivnig it more.. the miss seems to have gone away.. but I think as a result of running all of the unburned fuel through the CAT.. it popped a PO420 code. Poking around on youtube.. there are several techniques to clear this code.. some that just replace the CAT converter, but others have been efforts to clean the existing converters. One technique was to remove the O2 sensor and spray in half a can of Seafoam into the converter. This worked for that guy, the code cleared and didn't come back. The most interesting one is to pour a gallon of Laquer Thinner into the gas tank with about half a tank of gas.. or 10 gallons of gas. After pouring in the thinner, you drive the car at freeway speeds and run that 10 gallons of fuel out.. about 150 miles in that case.. and it also clears the code. There were several videos that tried this technique on different engines and in every case except one, it worked. The one case, the CAT was damaged physically and not clogged up. I'm just curious if any of you wrench turners would have an opinion about doing this. Laq Thinner is a petroleum product, so no issue with it burning in the engine, and a $13 solution sure seems to be better than the cost to replace the CAT. All comments appreciated.
BD


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ShipFixer
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Joined: Sun May 24, 2009 9:52 am
Location: San Diego, CA

Postby ShipFixer » Sat May 09, 2020 9:29 pm

Don't know about laquer thinner and whatnot... :?

But maybe start with the usual culprits. I cleared a 0420 code at Christmas by changing my spark plugs ASAP. No cat damage, no codes around six or eight thousand miles or so later.

At 114K if you've never changed the plugs, it's time?

TooMuchControl
Posts: 335
Joined: Tue Apr 28, 2020 4:41 pm

Postby TooMuchControl » Mon May 11, 2020 6:25 pm

I tried the thinner, didn't work. Scotty Kilmer thing.

Does it give a code for the misfire? I would think it should? Maybe check if you have a pending code that clears, perhaps.

I like the idea of changing the plugs....it's simple and would eliminate part of some free testing / checking.

I'm thinking short and long term Fuel trims on Bank 1 and Bank 2 would identify a problem between the two banks, if there was an issue on the fuel side where you have a misfire.

The misfire and the CAT code could be completely unrelated as well. It could just be a bad CAT and you have a misfire. Why the spark plug change makes sense...


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