2006 Tacoma 4.0 with repeated P0420 and P0430 codes and rich fuel trims.

I have replaced my 2 front Catalytic converters and 2 new a/f o2 sensors. I keep getting P0420. & P0430 codes. No exhaust leaks. Smoke test shows no vacuum leaks. However they keep coming back with rich fuel trims. Any suggestion. I also switched to 93 octane fuel. Here is a vehicle scan with live data.


https://resources.repairsolutions.c...8ee-4fb5-8d2a-18e9eb928761_03192025100240.pdf

 

So you need to graph the upstream and downstream sensors. Then trigger a vacuum leak, see how long it takes for the down stream to change.

There should be a delay, the delay is the catalytic converter reacting and changing the chemical compound.

P0420/30 triggers when the ECU doesnt see a delay from upstream to downstream when there's fuel trim changes.

Basically its likely you have aftermarket cats and they've failed already.

If you're not in an emissions state I'd suggest this next.



It's hard to find, but an o2 sensor spacer/anti fouler tricks the ecu by inducing a delay. I've installed them on buddies 4.0 before and it solved the p0420 right away. It has to be curved/90 degrees.

 

Thanks for the info. I failed to mention i have the passenger side o2 in two bungs in attempt to trick it.

 

Great info but I see no need for the curved anti-fouler, lots of guys on here using the typical straight ones including me and it's eliminated 100% of the P420/430 codes for a few years now. It got to the point where I was getting a 420/430 almost every time I drove the truck, Installed the anti foulers and I haven't seen those codes since.

 

Cheap o2 extenders often fix po420, po430 what brand new aftermarket cats won't!

Blame the epa overregulated overstringent/unrealistic demands put on the system

 

What length and thread pitch are the spacers supposed to be? I think I might throw some on mine too. I’ve had 0420 since I’ve owned my truck and refuse to pay $1k for new cats lol

 

Not sure on the size. I ordered anti-fowlers from Advanced Auto parts, they sent them down and I drilled a half inch hole in them and installed them only on the passenger side. I need to add one to the driver side.

 

You only put them under the downstream sensors don't put them under the upstream ones.

 

Just to confirm, that is the ones that are after the back converters and not the front a/f sensors.

 

Correct, if you put spacers under the upstreams it won't be able to control fuel properly.

 

Thanks for the help. It’s greatly appreciated!

 

That's exactly what I did