BigJohn

MY check engine light came on and i pulled the code P0420 Cat Efficiency below threshold B1 anyone know what this problem would be? I do have a aftermarket exhaust which has a hole in it maybe that is the problem

george16

Is the hole before or after the cat?

BigJohn

after on the muffler

revenantdead

should have nothing to do with an 0420 try cleaning the MAF and the throttlebody. clear the code. see if it comes back. if it comes back you may need to change an 02 sensor.

BigJohn

i heard that 99% of the time when you get a p0420 code its the cat and not the 02 anyways if it is a 02 is there a way i can test it do i need a special tool? how much does a new 02 cost?

fish0281

Yeah, it's pretty likely it is the cat, especially if you have any sort of higher mileage.

You can get the best prices on DENSO AF and O2 sensors on amazon - part numbers can be found either by searching the forums or looking it up on URD's website.

I've been dealing with a P0420 for a while now and I've narrowed my problem down to the cat after cleaning the MAF/TB, replacing both sensors, and general tune-up stuff. Toyota CCs are super spendy, but aftermarket ones seem to be pretty junky... Keep us informed as to what you end up doing!

Kiroshu

Normally when code P0420 is seen alone means there is more than likely an issue with fuel trim/air-fuel ratio and fuel burn time, If air/fuel ratio and burn time are ok then more than likely the catalaytic converter has deteriorated some due to a previous issue in air/fuel ratio. <--- Like a miss fire or a faulty sensor.

Its possible for this code to trigger due to improper grade or quality of fuel.

First and easiest step is to replace spark plugs.

Second reaplace post and pre-catalytic Oxygen sensors Bank 1.

After that and the code re-appears you may be looking at the Catalytic converter.

BigJohn

i only have 111,000 miles im gonna get a new muffler maybe thats the problem

skoti89

im pretty sure all of the above posts said it is most likely the cat. I replaced the cat on my brother's 97 taco 2.7 and it fixed the P0420 code

j-man

has nothing to do with the muffler. search po420 here, on tacoma territory, custom tacos...etc and you will find your answer. good luck

maf cleaning, front 02 sensor, plugs....are wayyy cheaper than new cat.

revenantdead

make your own decisions, however try what i said and then what he said and i'm pretty sure you wont see it again. just my .02c. do with it what you will.

PismoJoe

You guys are going way too deep on this one, it needs a cat.

pmow

Got those codes, and the p0133 is bank one...
Dealership estimated Cat replacement at over $3,000...
But when I checked the O2 sensor, someone had taken the nuts off the mount, and it was hanging loose (dealership/stealership)...
Should I just replace the O2 sensor, with new nuts tightened down and see what happens? If so, any tips on disengaging the O2 from the wire harness is appreciated... it's tricky up in there ;-)

JBSTRD

I had a P0420 on my Cali emission 2000 4Runner w/3.4L. I replaced the rear O2 sensor, then replaced the two factory Cali emission cats with two aftermarket (Magnaflow) cats. The factory ones are better, but they cost about 5-6 times as much. Anyways, since the aftermarket cats are not Cali compliant, the engine light came back on as expected.

To fix that issue, I purchased the URD O2 sensor simulator. This took care of the engine light and I know my cats and rear O2 sensors are good despite the engine light coming on.