Coincidence?

[FMFwarrior]

I've had this 4runner for just over a week and put a few hundred miles on it. No CEL the whole time. I change the oil over to mobile 1 high mileage and as soon as I turn it on, CEL turns on and throws an emissions code for bad catalytic converter. Does this always happen on 4runners? My plan is to erase the code and hope it never comes back. If it does, I will change the O2 sensor and hopefully that will solve the issue.

 

[thegipper]

Check and see if the cat is clogged

 

[JayRolla]

I've had this 4runner for just over a week and put a few hundred miles on it. No CEL the whole time. I change the oil over to mobile 1 high mileage and as soon as I turn it on, CEL turns on and throws an emissions code for bad catalytic converter. Does this always happen on 4runners? My plan is to erase the code and hope it never comes back. If it does, I will change the O2 sensor and hopefully that will solve the issue.

Pure coincidence. Rear o2 sensor I'm guessing. Could be bad cat.

 

[A.Wilson013]

I've had this 4runner for just over a week and put a few hundred miles on it. No CEL the whole time. I change the oil over to mobile 1 high mileage and as soon as I turn it on, CEL turns on and throws an emissions code for bad catalytic converter. Does this always happen on 4runners? My plan is to erase the code and hope it never comes back. If it does, I will change the O2 sensor and hopefully that will solve the issue.

What's a bad catalytic converter code? P0420?

It's either a coincidence, or perhaps you knocked a vacuum line loose while messing with the filter? Your emissions junk is on that side of the engine bay (if it was attacked from above).

 

[Johnate0]

Any chance you overfilled with oil?

 

[BerryP]

Coincidence yes

 

[FMFwarrior]

Any chance you overfilled with oil?

Dip stick shows oil levels are perfect.

 

[jgue467]

That is why the word was created!

So what specific code did it set?

 

[FMFwarrior]

That is why the word was created!

So what specific code did it set?

P0420 was the code. I think I thought of the culprit though. I ran some seafoam through it. From my understanding it can cause a CEL. Hopefully that's all it is.

 

[mtbtim]

Like others have stated, it's probably coincidence. However, looking up the P0420 code, I did read that oil contamination is a possible cause. What kind of contamination they're talking about, I don't know.

I've now seen the P0420 code on a couple road trips. Maybe it has something to do with changing elevations (which in turn means changing oxygen levels) and the computer doesn't respond quick enough and it throws the code. During my last 3000+ mile road trip to Idaho, Oregon and back home, I cleared the code twice. It hasn't come back. Before this recent trip, the last time I saw the code was a couple years ago on a road trip to Utah, Colorado and back.

But like you already said, hopefully you'll clear the code and won't see it again. If you do get it again, I'd replace downstream O2 sensor as a first step and probably replace the upstream one as well.

 

[shahsmerdis]

Before blindly changing O2 sensor, test it out to make sure values are about what they should be. Plenty on youtube and pretty straight forward to test Of my understanding rear o2 should be pretty constant if CAT is working correctly.

https://www.youtube.com/watch?v=DvKZ2GDYEz4

 

[Buckaroo]

I've had this 4runner for just over a week and put a few hundred miles on it. No CEL the whole time. I change the oil over to mobile 1 high mileage and as soon as I turn it on, CEL turns on and throws an emissions code for bad catalytic converter. Does this always happen on 4runners? My plan is to erase the code and hope it never comes back. If it does, I will change the O2 sensor and hopefully that will solve the issue.

The P0420 code sets on two trips. If you checked the pendiing codes with a code reader prior to purchase, you might have seen it from the get-go. But now, after the fact it lights up. You might get lucky with an O2 sensor but likely you are buying a Cat if you need to pass emissions....Sorry.....Not the worst thing in the world, just a lesson for the future reinforced by spending some $$...

Good luck,

Buckaroo

 

[jeremyc74]

Mine will throw a random P420 code from time to time, and when I reset it doesn't come back for months.

The strange thing is it seems to do this when I make long road trips and the weather changes quickly (like going from FL to IN in the winter time). I suspect that either the rapid decrease in IAT throws the fuel trims off enough to trigger the code, or the change in fuels from summer to winter does it.

I don't have any real data to back that up, other than the fact that I've seen the bong hit code come up four or five times, and always after I've made that trip one way or the other. If the truck stays in FL, I never see it. When I leave it in IN for months, I never see it.

So I reset it and forget it.

 

[TheDurk]

My guess is it's not coincidence, but nothing to do with the oil. Could be the seller cleared codes to get the CEL off before you bought it, and the week's driving was the time it took for the test to complete (twice) and set the CEL on. ALWAYS scan a used truck before you buy it. If the tests aren't complete, run.

 

[Road Bull]

I got the same code about three weeks after I picked up my 4runner. I replaced my rear O2 sensor and it went away shortly thereafter after. Now it comes and goes, but at least twice now, it has come on after I cancelled the cruise control on the highway. Now I know that they are more than likely they are not connected, butter it still makes me suspicious. Lol.