Argh - P0420 and a few questions

So my truck threw a P0420 code about a week and a half ago. Looked it up, said catalyst system efficiency below threshold. Ok, no big deal, cleared the code. I had just put a full can of seafoam in the half tank of fuel I had left so I thought maybe it was related so just cleared it. Then I was able to drive @ 125 miles and then it kicked it again today after driving less than 10 miles on a full tank of fuel (no seafoam this time) Anyway my question is this....is it ok to keep clearing the code if it comes back? Is it going to affect anything to run it like this?

I think it has a newer cat on it so I would be surprised if that was the issue. It did sit for 5 years and has only been on the road 2.5 weeks so maybe I just need to drive it more? Other thing I noticed is when its hot out and I shut the truck off and come back @ 15-20 mins later it has to crank for 3-4 seconds before it will start. When cold it starts right up with a second or 2 max, but when hot it cranks a bit longer and kinda stumbles when it starts. Could that be related?

Thanks

 

http://www.customtacos.com/tech.old...06toyrm/06toypdf/06rmsrc/rm2006ta/0060035.pdf

 

The infamous P0420 code can be caused by a lot of things, all of them emissions related. Leaving it on won’t harm anything, except you won’t know when your CEL is on for a legit problem. When my Prerunner threw that code, it kept coming back, so I ran a bottle of Mr. Gaskets Cataclean through my gas tank while it was real low. I don’t usually believe in gas tank additives, but I can tell you after running it through my tank, I never had another P0420 code. In fact, it even showed it was in the ready mode for an emissions test.

 

From the PDF @BillsSR5 links above, trouble areas

Front exhaust pipe
•
Gas leakage from exhaust system
•
Air-Fuel Ratio (A/F) sensor (sensor 1)
•
Heated Oxygen (HO2) sensor (sensor 2)

1&2 are mechanical and shouldn't be too hard to detect if the problem.

I'd bet on the HO2 being bad.

But the only way to pick / chose between the sensors prior to changing that I'm aware of is connection of OBDII software that will monitor the dither rate of the devices, and show you which is out of spec.

There's nothing wrong (other than polluting more) with resetting and continuing to drive 'in case' it self clears for some reason. Not impossible, but I'd not bet my lunch on it either.

 

I had the p0420 code on a 2004 Tacoma trd I changed sensor1 and sensor2 these are a good place to start especially if u have over 75k miles on the originals

 

Ok so it might cause it to run rich then even after I clear it?? Its a 2RZ-FE by the way.

I dont notice an exhaust leak, sounds pretty quiet to me. In the records book from the PO there is an entry where he wrote "got a new catalytic converter to silence check engine light" And that wasnt that many miles ago. I dont know if my pocket OBDII scanner will tell me that stuff, I am thinking not.

I have 186,000 miles, and yeah it wouldnt surprise me if they are originals. Rock Auto ok for O2 sensors?

 

changing the cats is the most expensive option, I would start with changing sensors 1 and 2, where ever you get the sensors make sure you get DENSO brand! if you search in GEN1 forum for p0420 codes u can get a lot of infos its a prevalent issue with high mileage gen1s.

 

It seems to me like your truck is trying to tell you it's time smoke a joint.

sorry I have nothing to add. Hope you get it worked out OP

 

For sure will get Denso. Ok I will do a search too. It doesent really worry me, just more of an annoyance. I hate having the CEL on because then if something important happens I wont know.

I might even try running some cataclean stuff through it when I get down to 1/4 tank or so. And maybe take it on a decent highway run, havent been out of town yet really. Might be good to strech its legs and run it a bit at 70 mph. Been getting 22-23 mpg around town though so that seems pretty good to me.

 

I had to clear the code numerous times after changing out the 2 sensors and it finally stopped coming on,i had a bottle of catylclean as a backup never used it, also exhaust leaks could throw these codes too