Throwing Code: PO420

I tried cleaning my MAF, checked the condition of the O2 sensor, tested the resistances and voltages of O2 sensor, checked spark plugs, checked exhaust for leaks, ran Chevron Techron fuel system cleaner with 93 octane gas through it, still get the 0420 code.

 

I got this code a couple of times when I started using Conoco 91 Non-Ethanol
I've been using Chevron 92 E10 for about 2 months now... haven't seen it since
Could be a coincidence... but, thought I'd throw that out there

 

I guess that after I make my insurance payment, I'll save up and get the upstream O2 from Rockauto. Cheapest place I've found so far. And I'm going Denso, because I hear that our Yotos don't really take to Bosch and many of the others.

 

Check out URD's o2 simulator, I used it when I took my cat off after getting stolen twice. No check engine light and no cat, so there a little bit better throttle response, not much but the main advantage is that your cat wont ever get stolen.

 

Put a new rear O2 sensor on, went for a drive and watched the catalytic converter monitor. The ECU tested it and gave it a "ready". Before this, it would not go to ready until two faults and a CEL. I think my problem is fixed.

 

Gets new cat.

P0420 very rarely lies. The only reason that code comes up is because your cat isn't doing its job.

 

If it comes back I will take care of it. For now, replacing a 9.5 year old, loose, rusted, 174k mile rear O2 sensor seems to have did the trick.

 

I have been flirting with p0420 for a while after blowing a motor through the exhaust. After barely passing my last smog check I have been doing a little testing. No exhaust leaks, but via live data my front air fuel sensor was lethargic and very slow to respond. It was replaced which did help a bit with drive ability but did not stop my p0420 code from showing up. After talking with a few ex smog techs I work with they asked what my inlet and outlet temps were on both of my converters. I was not aware until that point that under acceleration or load after warm up that the outlet temp should be at least 100 degrees hotter than the inlet temp. My rear cat shows almost a 200 degree rise in temp, my front shows a drop of about 50 degrees. This tells me that my first cat is not lighting, and thus not doing its job causing my code. A new california legal cat is on its way to hopefully fix this issue once and for all.

 

Nine days after replacing my rear O2 sensor and I'm still 0420 code free. Did you check your rear one? It's tough using an infrared thermometer. I tried that early on and got different temps every time.

 

The light has been on for a while, but yesterday my negative terminal slipped off (It does that sometimes) and when I took care of that (put a nail in there to solidify connection because the terminal is already as tight as it will go) the light didn't come back on. Almost 200 miles since that time yesterday, and still no light. But I ordered the new upstream o2 from Rock Auto, just haven't been able to install it yet.
Definitely liking Rock Auto- cheap, on time, and they even sent me some cool fridge magnets of cars that people have rebuilt using their parts.

 

Been fighting p0420 for sometime. I found running a higher grade fuel (89) keeps the light from coming back as soon. It's becoming more frequent as time goes on, which leads me to believe, from everything I've read so far, it's the cat or cats. I've got an '02 2.4l with 180k, only recently developed this issue, started last year about October and has happened a handful of times since then. Usually extended interstate driving seems to throw it.

Not throwing any other codes. Tried non-ethanol 87, didn't work. 89 kept it at bay for months only kicking once or twice. I changed exhaust manifold gasket and the 1st doney below it. Neither were blown. No exhaust leaks that I can detect. Pre and post dual cat systems suck.

Anyone have luck running 02 sim and chopping both cats in favor of test pipe?

 

Check your O2 sensors. That fixed mine. The rear one had 175k miles and was hanging by a thread...literally.

 

Where is the rear one? I only saw one under my truck and it was right before the first cat...is tje up stream on the header?

 

You noticed the corelation with the interstate too? Each of the three times my light has come on, I was on the interstate for an extended period of time.

I'm trying to replace it as soon as I can, but the nuts are so rusted and stripped (DON'T EVEN MAKE A JOKE, LOL. I ALREADY CAUGHT THAT.) that I'm going to have to either cut them off or file them down enough to get a 10mm on it. Either way, it's gonna be a nightmare. I've been soaking them with PB Blast. Spraying it on them every couple of hours so they will hopefully come off a little easier when i get around to it.

 

So I finally got around to changing my forward catalytic converter today. When I dropped it out and looked inside I found all that was left was a little cone shaped chunk of catalyst about 1/4 the size it should have been. The rest was shredded and piled in front of the rear catalyst bed.

The rear one looked a bit eroded. I hope it still functions correctly as it is a little late to test it tonight.

 

Wow! That's nuts!
I still haven't been able to mess with mine. Between working, home, and everything that's happened the past few months, I've been hard-pressed to find the time.

 

I put my stock intake back in this morning and cleared the code in memory. I ran around with torque for a while watching my o2 sensors for a bit. Now to hope my monitors all set and hold for my upcoming emissions test. I hope the rear cat was not eroded too much by all of this.

 

I had a cel on and the cat was rattling so I knew that was probably the problem. So I bought a urd o2 simulator, put that on and the cell went off. We took the cat off completely and just put a pipe in. It runs so much better.

 

Is that legal, though?

 

What improvements have you noticed? I'm pretty sure my cat is the P0420 culprit, considering taking it off and driving to see if I notice a difference.