P0420 troubleshoot

2000 is a transition year so your front sensor could be a/f or O2. If you talk nicely to the oriellys people you should be able to get them to use their code reader to livestream sensor outputs on a graph. When I had vehicle issues awhile back the guy was nice enough to do all that and he was using the best reader they sell.. I bought the second best after that and it does it as well..


I'm guaranteed to need a new cat because my rear O2 sensor output jumps up and down like the front one. I have no performance issues what so ever and you couldn't tell the cat is bad if you rode in it.


I honestly believe the crack in your exhuast pipe is the culprit. Any exhaust leak up front of the sensor can cause that code to be thrown.

 

You have to check the emissions sticker because the 2000 V6 3.4L were manufactured California emmisions and Federal emissions.
Cali models have A/F B1S1 sensor
Federal have O2 B1S1 sensor

 

I’ll try that tomorrow. Just to clarify it’s a leak between the two sensors. To be specific it’s right at the weld of the start of the second cat.

 

when I looked up on sensor the front is called the air fuel sensor. I’m pretty sure I got the right parts.

 

Here is the part numbers I used for my truck.

 

I have a single cat system so I don't know if they act the same but it should be that if the leak is before the last sensor you can get a P0420 code

 

good to know I will update in a couple days after I’ve sealed the leak. Assuming that’s the only one I find.

 

That could be your issue causing the code. A leak before the rear o2 could cause it to see a mixture that triggers the faulty cat code.. I would fix that leak, clear the code with an obdII scanner and see if it comes back

 

If the computer sees that there’s an unexpected difference between the front o2/af sensor and the rear one, it will deduct that theres an issue with the catalitic converter and throw a logic code. In this case, the rear o2 sensor is likely (accurately) reading the unexpected excess oxygen pulled in through the leak. I can’t stress enough to fix the leak before throwing money at it. Even some of that exhaust tape they sell just to check the issue. You’ll need to make sure your cat monitor has run before knowing for sure that it has worked.

to summarize, fix the obvious problem before diving into the other stuff.

 

Currently waiting for the patch to dry. Then hoping to borrow a buddy's shot vack check for any other exhaust leaks.

 

You can also use an electric air mattress pump too. Good luck and let us know how it goes!

 

I'm soaking my rear o2 sensor in carb cleanse right now. No idea if it'll fix it but if it does then $5 well spent. If not then I'll try a spark plug non fouler. Then if that doesn't work I'll have to consider the cats or a leak I guess. The AF sensor isn't very old at all so it's not that.

 

Welp that didn't work but apparently I can solder some resistors or some shit to the wiring to trick it according to the 3rd gen runner dudes so I'll do that next

 

How complicated is the cat replacement on an 05’ DCSB 4x4? I was just quoted 4K for replacement parts, and I’d like to fix the CE light and increase my fuel mileage! Getting codes P0420 and P0430, replaced both downstream O2 sensors, and the problem persisted. I’m going to check for leaks tonight. How do I know if it’s the upstream or downstream cat?

 

The replacement isn't that hard, I don't believe (unsure if you'd have to bolt one on or weld it), but the materials are costly making them expensive right now. Thus the reason they're being stolen so frequently right now.

 

I ordered a URD O2 sensor modulator. 99% sure my truck will still pass sniff test in my county even with a manipulated O2 sensor. The resistor mod looks like it only works sometimes. I'm not gonna bother.

 

Took all of 10 minutes to install this URD sim. Got the code cleared now just need to drive it around a while and hope it doesn't come back

 

So far so good, no more P0420, I swear I'm getting better MPG too, but haven't confirmed.