How do I mend a P0420?

Was having some issues yesterday while at work. Got it home, but I didn't want to drive it until it got checked. My parents mechanic came by while I was at work and gave it a look. Told me to look up a Code P0420. I know it has to do with the Catalytic Converter. And that's about as far as my internet search has gotten me. In all efforts to avoid having to replace it, how can I check the Converter, and what tools do I need to do that (other than wrenches lol).

I've had the truck almost a month I think. I've changed lights, and learned how/helped to change the belts and that's as far as my knowledge takes me.

On another note I've ordered the Master and Slave cylinders as they need replaced, and would like to know how to change those as well.

Any and all help is appreciated.
Thank you.

 

Look into your upstream O2 sensor..PO420 is bank one 1 sensor I believe..so its your A/F sensor. You can check resistance of the heater circuit pinouts to see if their within spec of FSM. You'll need a multimeter.
If scanner tells you more, and it happens to say bank one 2 then its your downstream sensor(cat effiency monitor)

 

Did you manage to get the P0420 code taken care of? What was the fix?

 

P0420 is for sure the A/F sensor. As said earlier bank one sensor one. Had the code on my 01 4runner with the 3.4 and the a/f sensor fixed it.

 

I was at work when my buddy fixed it for me. I wish I could have been there but I believe it was just a sensor error. The lights been gone for a while now.

 

Funny thing happened to me. I've had 0420 for many, many years. Tried a lot of fixes. Nothing worked. Gave up and decided to live with ti. Whenever I would disconnect the battery or clear the codes, it would show up again in a few days. Sometimes immediately, but usually a day or so. Until I had this problem:
https://www.tacomaworld.com/threads/wont-start-until-battery-disconnect-reconnect.683894/
The fix was to replace my battery cables. Positive and negative. It's been over a month and no CEL and no 0420. Weird fluke? Or could this have been the cause of 0420, which I would not have thought was related at all?

 

isn't P0420 the catalytic converter on its way out? I get this sometimes when wheeling now, high revs without much load on the engine. As soon as I get done wheeling, I clear it and it doesn't come back until I go wheeling again. I'm not gonna worry about it until it starts popping up a bunch under normal driving conditions.

 

Yes, P0420 usually points to a bad cat. People that say it's gotta be the A/F or O2 sensors are just in denial of the fact.

Or it's a leak in the exhaust before the sensors somewhere

 

Yea, it /should/ be related to that. But I had replaced the catalytic converter and both oxygen sensors. Mine comes up under normal driving conditions, unfortunately.

 

P0420 usually comes and goes like that, certain driving conditions are more likely to set it off and sometimes those conditions don't happen and it doesn't come back for awhile. That's exactly how mine was for months, eventually it started coming on and staying on longer though. New cats got rid of it for good.

 

Also if you disconnected your battery, you reset the emissions cycle and any codes that were showing so they will be gone until the emissions cycle completes again and the code comes back. It will be back

 

what the heck? I thought a new cat/o2 sensors fixed this. Did you replace the AF sensor also?

 

"It will be back"
Ugh. Ok, probably a false hope I had.
No, no new AF sensor.
Maybe I just got a crappy aftermarket CC when I replaced it and didn't consider that at the time.

 

Sorry I missed where you said you replaced the cat already...what kind of cat, do you remember? I would imagine some less expensive aftermarket ones don't have enough of the material in them that filters the emissions so the sensors still see them as bad cats. I got mine replaced with Magnaflows, CA approved ones because I have to pass smog every 2 years. That took care of the code for me

 

Of course there are Toyota/OEM cats too but those are crazy expensive, which is why I went with Magnaflow. I also hear Walker makes a good aftermarket one

 

how many miles on the magnaflow? I may go that route when the time comes. Not dropping $2k or whatever for a fucking catalytic converter lol

 

At the time I got them done 3 years ago, I got both replaced front/rear for $600 out the door at a local exhaust shop. I heard though recently that prices on cats have gone up quite a bit due to the material in them getting more valuable. Still way cheaper than OEM though

As for miles, I have about 40 - 50k on the magnaflows right now

 

solid endorsement!

 

just went back and edited a bit, it was actually 3 years ago because it was right before a smog test and then I just had another test last year...so 3 years. But yeah for the price I feel it's been worth it, even if they don't last as long as OEM normally do which I'm sure they won't. OEM is the best quality but you pay out the whazoo for it

 

No. Oddly I have the warranty, but didn't keep the receipt. I usually keep everything, but this slipped through somehow. Replaced it in 2012-June. 80,000 miles ago. Probably the cheapest option from Autozone.

Is 80k miles a lot for a CC? Feel free to mock me for this question. I can handle it.

Downstream O2 sensor replaced 80,000 miles ago. Upstream O2 sensor replaced 30k miles ago. Those things should last 100k miles, right?