PO420 Again... I know but...I did read all the other forums but this one is different.. wait for it

I chased this same squirrel on my 2012 2.7 after buying it. Replaced one sensor. Replaced the second sensor. Finally got the sensors working properly so the truck could finish it's diagnositic checks. Once it could, it reported the cat efficiency was crap. I bought the blueDriver OBDII scanner that reports actual values to my tablet...and the efficiency number was not "borderline" it was terrible.

$75 BlueDriver Bluetooth Pro OBDII Scan Tool for iPhone & Android - No Subscription Fee - OBD2 Car Scanner and Code Reader - Diagnose Check Engine, ABS, SRS, Airbag & 7000+ Issues on Vehicles 1996+

https://www.amazon.com/gp/product/B00652G4TS?ie=UTF8

Anyway...then I put my VIN into the Toyota site where you can check for outstanding recall campaigns and I'll be darned if it didn't come back showing a recall for bad cats that had never been completed by the previous owner.

BaddabingBaddaboom...local dealer replaced the cat assembly FOR FREE.

Some times it's better to be lucky than good.

 

.and the efficiency number was not "borderline" it was terrible.


I have a scan tool that will allow me to see all the PIDs and their names. I do not recall a PID that said anything about efficiency but I can't say that i was looking for it explicitly.

Do you have to know which PID it is that you saw that did that summary?

 

Sorry. I do not. I'll check next time I hook it up again. I'm 99% sure it was under the Bluediver's "Mode 6" page

I think this will explain it better than I can.

https://support.bluedriver.com/support/solutions/articles/43000582819-mode-6-introduction

 

As bishop mentioned, look at oxygen sensor responsiveness. Generally speaking, if there's no exhaust leaks and the 02 sensors are working then the cats are bad

 

Yes that is correct. Sensor 1 = Upstream Sensor 2 = Downstream Bank 1 refers to the side of the motor that the #1 cylinder is on which for us is the Drinkers side.


I also wanted to give you all an update. I spent a good hour last night with the scanner. Pulling vacuum lines off and checking for responsiveness. In my case I am not seeing a big change or delay looking at the readings from Sensor 1 or Sensor 2... when I graph them out I had one pegged at 3volts the whole time and didn't move and no it wasn't the heater value. I had one stay around .06 to .08 on the downstream side and move a little ... i am not happy with the data i am getting at all. It is not conclusive. There is data they are connected but it quite literally is all over the graph.

This leads me to think that either I got defective sensors from Rock Auto or this might be an example of this thing not liking Bosch Sensors. I ordered Denso sensors they will be here next week.

One of two things are going to happen, I am going to prove that the Bosch sensors are the culprits and it goes away or I am going to get the data to be consistent and prove that the cats are indeed done and need to be replaced.
The good news is that at least I will have new O2 sensors.

I will update more when I learn more.

 

Thank you

 

Update: I still do not have the new sensors. they have been delayed. No news at this point

 

Thanks for 'checking in'. Too many show up looking for help and fade off into the hinterlands, never to be heard from again
.

 

3/7/2022 Update All four sensors were replaced with DENSO the appropriate part numbers from Rock Auto.
After replacement checked the data from the PIDs for AF Sensor and O2 Sensors. I would pull the Vacuum Line off the brake booster to change the AF mixture
I noticed that data values were changing and different front to back. There was a delay in the change from Sensor 1 to Sensor 2 per bank, they looked pretty good to me. Now as there enough difference to get me out of the efficient error WHO KNOWS.

I ran the truck for 2 days with the Codes cleared.
On the 2nd day. MIL = ON (check engine light on)

Now I am getting 2 codes:

P2255
P2242

At this point, I think I want to burn it with fire....

What I think has happened here is that I either broke a wire on the Bank 2 Sensor 1 AF sensor or I did not get it plugged in correctly.
It is odd that I saw data and it read at least some changes I have no idea if it was "GOOD" Maybe it vibrated off.

I have a couple of things....

1. If I find the engineer that put the steering shaft right in front of the wiring harness for the AF/O2 sensor... I am going to kick him in the no no square.
2. We can put a man on the moon but some how wiring harness connectors have to be connected with a magical connector that a grown man can't squeeze and release with some sort of ease was a bridge too far.

Here is what I am afraid of. I get back under there find that I either broke a ground wire or didn't plug it up right.... (which how I don't know.... it only goes on one way) but once I break the great urge to burn this thing to the ground..... I am going to get that wiring issue sorted and 2 days later after the full test runs, I am going back into the low effency cat issue and have to replace the cats.

Do you all think my assumption of the current state of affairs P2255 and P2242 is valid....

It is going to take a couple days for me get the courage to tear into it again, but I will update then too.

 

Update 4/11/2020
Ok so time got away from me for sure. I let my daughter drive the truck until yesterday afternoon and I finally drew up the courage to take Bank 2 AF 1 out... Sure enough it was dead. No resistance there was a healthy dent on the upper section of the metal housing. I am going to equate this to my cave man strength and dinosaur brain. I must have slipped the O2 Tool and gave her the ole Heave ho.

So I installed one of the Bosch sensors. She has driven the vehicle for about 30 miles no code yet, I am going to say yet because I can't tell for sure if its run all the tests, last time it took a couple days.

So I am going to run it see if I go back to the condition where I get the low efficiency cat performance codes on both banks (i suspect that i will) Will let you know.

 

You screwed up in buying the Bosch sensors. They are garbage. Confirmed many times over.

To make matters worse, you went back out and bought 3 more Bosch sensors.

I'm not kidding. They suck. Go for Densos and you will have to recheck, as they will work accurately and nicely with the OE computer. If you need a cat or two afterwards, well, then you're going to need them, but at least you'll have an accurate slate to check on.

 

You know I get that, but the bosch ones are more expensive than the Denso, and if there is a hard requirement to use Denso, then why did parts counter give me an option to get the Bosch sensors. This is the first Toyota I have ever owned who would know this without getting hit in the face with it. Probably a rhetorical question and i am sure it will start an argument. Given the data that I have. Now if I run this for a couple weeks and the codes stay clear then it would be pretty firm proof to stay away from Bosch. It is just a pain in the butt...


I will update when i have more data.

 

Denso Spark Plugs over NGK when time replace the spark plugs as well. I believe bank 1 is Denso, and bank 2 is NGK from the factory......

 

It’s actually easiest to reach that one from underneath the truck. You can see it and a get a hand on it easily from underneath.

 

OK Final Update 4/12/2022
So after replacing the O2 Sensor Bank 2 Sensor 1 (which for those of you that do not know is known as the AF (Air Fuel Sensor at least in my MK808 tool)
So I had to replace that O2 sensor because I broke the O2 Sensor. I broke it on install, which was all my fault the O2 removal tool that I used slipped and hit the top of the sensor where the wire comes in and broke one or more of the wires. There was no OHM readings on any of the terminals or ground of the sensor.

At this point I replaced the brand new DENSO O2 sensor with the Bosch O2 sensor that I removed which was new. I swapped it out because of what I read online about requiring DENSO (from the original issue)

As of today all of the I/M readiness checks are complete and all 9 of the 10 that I have for my model are in an OK status which means I have completed a full drive cycle. The 10th one is N/A.

At this point I am going to continue to drive it and and consider it repaired until something else changes.


So what I have learned and in conclusion.
1. Denso sensors matter on the #2 or the Back Sensor.
I say this because when I replaced all four of the sensors with the Bosch Sensors, the ECU threw CATA low efficient performance codes until I replaced them all with the Denso sensors
2. My example is that a Bosch censor will work in the Sensor 1 or (AF Sensor)
this could be my scenario but those are the facts

3. Don't be a ape and get angry at the O2 censor and break the wires off it.

4. If I had to do it all over again I would Put all Denso censors into the thing just to prevent rework although I think this test would indicate that maybe in the front Bosch will work.

5. I still stand by my statement that the Bank 2 Sensor 1 is the worst and it takes both going thru the wheel well and under the truck to get it off.... The engineer that designed that should get kicked in the no no square.
I have done this O2 sensor 3x and that is what worked for me. the rest of them are fairly easy to get to and reachable under the truck.

6. EODB is your friend some times simpler is better. I use an MK808 Autel scanner with Toyota specific decodes there were simpler view thru EODB that show things like ranges of the PID Data on each sensor and what the acceptable range is, and the I/M readiness summary....
That is my experience yours may vary. Miles will vary. I did not hate working on this issue enough not to help my neighbor for beer, but he gets to do Bank 2 Sensor 1.

Thank you all for all your help and advise.

Hope this helps someone

 

Thank you for the update. Honestly if all anyone ever gets from this thread is only buy and install Denso sensors on your toyota you will have made a difference in someone else's life.

 

Yep. 63K miles on my 2014, long way from needing O2 sensors.. but when I do, they will be DENSO for sure.

 

yes, spacing the sensor somehow keeps it from making the check engine light come on.

there is even a spacer type male/female threaded thingy that i have used on several cars (with bad cats) to keep the check engine light off.

i do that so if you cel comes on, i know there's a different problem and it's not just the o2 sensor again

 

I just replaced all four of my o2 sensors at 185k with Denso. Got them from Rock Auto, was somewhere around $330 for all four.

 

My P0420 code turned out to be the gasket after the cat at the Y pipe.

It showed up shortly after a motor swap. My guess is the manifold and cats were not supported when they were disconnected from the heads.

It took a little while, but I found a mark of soot. Maybe an eighth of an inch wide at the top of that gasket connecting the Cat to the Y pipe.

Replaced both gaskets and the code went away.