check engine code p0420 bank 1

My check engine light came on today and I used an AAP reader that generated a P0420 code (bank 1) ... this notes an issue with the catalytic converter or related parts, such as the O2 sensors.

There's a 1st gen related thread -- https://www.tacomaworld.com/threads/need-help-check-engine-light-code-p0420.195841/ -- but I wanted to note my problem on the 2nd gen forum and I'm hoping to get some opinions and/or thoughts on my next steps.

I have a 2005 with 158k miles on it. The oil was changed 2 weeks ago and I added fuel cleaner 2 days prior to the light along with a fresh tank of gas. I've added fuel cleaner before but it's been many years and miles since the last one.

I have searched the exhaust for a leak and can't find one. The truck runs great (except I think I need to replace my wheel bearings ... different story). I don't notice any decrease in acceleration or responsiveness.

Could the fuel cleaner dislodge some gunk that could clog the catalytic converter (maybe that was a bad idea)?

Should I replace the O2 inbound sensor or both sensors? Or should I try to borrow an infrared gun or is there some way to validate the sensors are good? They've never been replaced.

Should I reset the check engine light and see if it comes back on before doing anything?

Are there other ideas to diagnose and try to isolate the root cause?

THANKS!

 

O2 sensor error. Just reset it and wait to see how long until it comes back. Mine does it every once in a while especially when it's cold weather.

 

If it’s a v6 swap the bank 1 and 2 sensors. See if the code follows. If it does you need a new sensor.

 

Thanks -- I'll try the reset tonight. If that doesn't work I'll go with the sensor swap. I'm heading out of town and will report back in roughly 10 days.

 

FWIW, if it ends up being a bad catalytic converter. Programs like hptuners can usually disable codes (for use in Offroad applications Incase the cats were removed all together)

 

I removed the code and at least today with 30 more miles it remained clear.

 

I believe what HPtuners does is merely make the DTC not display a CEL but if you hook an OBD2 reader, it will still show the code (if you're in a state where they check for CEL's for vehicle inspections). Another option would be to run something along the lines of a rear o2 simulator from URDusa. That tricks the computer into thinking that everything is good to go so no code and no CEL.

-J

 

It depends on how you do it. I have a c5 Corvette with long tubes and I have multiple codes turned off. You select no cel and no error reported (it displays no codes when scanned) was I’m assuming it works the same on the Tacoma, I just haven’t had a reason to use it on the Tacoma yet.

Edit to add: Although probably not worth it to most unless you already have it or a friend had it. It starts at like 400 dollars(the pro is more) plus 200 to unlock the ecm.

 

What's the point of this other than the PnP? The same thing could be accimplished with a 5 cent resistor.

 

I haven't personally used it either, it was merely what I read in the past. Perhaps the hw version at that time didn't allow for it but it could be an option for some. Definitely more expensive than the O2 sim but it looks like it has a wider range of uses.

I don't think it's quite as simple as a resistor, more of a voltage regulator tuned to imitate the expected signal of a properly running O2 sensor. Something around blockform 1.0v to 1.2v or constant 1.1v ... on a normal 02 sensor when the system runs its integrity checks about 5 to 15 min after the engine has been started. I don't have access to the FSM's anymore until someone else posts them somewhere to see the specifics. I believe URD has a universal o2 sim that has an attenuator that you can tweak to get your block-form to the expected signal but that's above my scope of understanding.

-J

 

In my case I used the ODB II scanner and deleted the P0420 code after ensuring the exhaust wasn't leaking. The code hasn't returned and I'll see after another week or 2 of driving. I'll be replacing the spark plugs next week. My best guess (or hope) is that the fuel cleaner triggered a mis-read on the O2 sensors which triggered the code.

 

if they are original it's the sensors. they end to die at this mileage. cats can be good for another 1-200,000 miles if they aren't clogged or broken inside
(I only do long trips my cats last f-o-r-e-v-e-r in 4runner)

swapping sensors is a PITA if you are gonna do
that just replace them (new nuts and gaskets needed just to swap them) or swap the cables (likely not long enough though)

 

There are three potential causes here..

The cat is really bad.

The O2 sensor is bad.
Or
The head gasket is failing.

Each one will involve different methods of testing.. the first thing you need to do is check sweeping activity of the oxygen sensor for the bank in question. Check the voltage. If there is a very fast sweeping motion from low to high voltage .100-.900mv you have a bad cat. Replace as needed.

Swap the sensors as previously stated if the sweeping pattern is pretty stable. If the code follows, replace the sensor.

If the above tests pass...
Time for a cylinder leakage test.

Let us know what you find.

 

I have the same code on my Camry