P0420/P0430 caused by exhaust leak?

I know an exhaust leak will cause these P0420 and P0430 codes, but will and exhaust leak past the sensors matter?

I have an air leak here, but I would think it could cause those codes… or could it?

 

I’ve been chasing these CEL problem for the past 2 months on my 2005 Tacoma (230,000mi). Came on after I bent the end of my exhaust pipe on a log and after I ran my gas tank empty. Those are the only reasons I can think of that caused it.

I cleaned my MAF sensor and throttle body, I replaced all 4 O2 sensors with new Denso sensors I got from Rock Auto, I took all 4 cats off my truck and cleaned/flushed them out and I can’t find any wire issues. Still both of these codes persist. Both codes come on at the same time and consistently after I drive the truck 50miles after I clear the codes.


My fuel trims seem elevated (anywhere from 7 to 11 at idle) and my gas mileage is not great. Seems to average 16 hwy

 

I was fighting the same issue for a long ass time. I did my spark plugs, PCV valve, downflow o2 sensors, a whole bunch of stuff (some honestly unrelated) and what turned my light off for what’s been about a month and still going now is fixing an exhaust leak I had. That could very much be it.

 

Where was your exhaust leak?

 

On the flange right before the downstream o2 sensor. I think it was a bad gasket.

 

No. A leak after the O2 sensor will not cause those codes.
Graph the sensors and see what is happening.

 

Alright I’ll get on that

 

@SR-71A had a similar issue

 

Based on year and mileage Id guess you are looking at new cats. But wont really know until you do some diag work.

As @fatfurious2 mentioned, the gasket you circled disintegrated on me last year. I did not get any CEL codes
Part # for my 2012 V6 is:

$30 17451-0A010 Toyota Genuine Exhaust Pipe Gasket

17451-0A010

 

I have seen in some rare cases, that the harness for the O2 sensors was inadvertently swapped side to side. This caused the same codes you have every time.

Looking at your truck, it looks quite stock so I doubt this is the case.

When you reinstalled the exhaust, did you install new crush gaskets between the header and y-pipe? New manifold gasket too perhaps?

 

Graph out your sensors are recommended earlier but tbh, p0420/p0430 codes are one of the few codes if not the only codes that are fairly reliable in telling you exactly problem, which is your cats are not converting enough. With your fuel trims being higher, spend some time to find the cause of that as an overly rich fuel mixture along with burning oil or coolant can lead to early catalytic converter failure.

 

Yes all new gaskets. Starting to sound like 230k miles made my cats obsolete. The cats honeycomb looks great and was still clean. Even though they look great, the platinum comb just gets eroded enough that it can’t help emissions?

 

I have similar problem, 420 code and rich mixture.2000 taco 2.7 AT and 371k. Runs great, poor mileage, etc. think about eliminating cat. What would be end result. I just hate the rich mixture and poor mpg. Thanks in advance for any thoughts.

 

Look for exhaust leaks. Fresh air confusing the oxygen sensors will drive the system rich

A bad cat will not drive the system rich. Eliminating it won't get you any gas mileage back

 

Thank you so much for frank and prompt reply. Would exhaust leak probably be before first 02 sensor? Around exhaust manifold maybe? Thanks again.

 

Why do these little 4 cylinder engines get such terrible gas mileage? Mine is 16 mpg city and highway combined!!

 

Yes upstream of the sensors or just in the general area. Look for black soot. Or shove a shop-vacuum (set to blow) up the tail pipe and spray soapy water on any suspect areas.

 

What have have you changed on your truck.....mine gets about 22/18.. besides, I'm ok with the gas mileage as long as it's as reliable as my 2.7l.motor has been.