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

Good morning,
I know that there are tons of posts about this but I think that mine is a little different. I have a 2013 Tacoma. I purchased on an insurance auction for mechanical issues. I bought the truck for my daughters first truck. I had to replace the motor with another 4.0. Saved the truck it runs and drives perfect. Its a good story and if you want to know the whole deal LMK.. Other wise off to the core issue for the week.

After about 500 miles, I got a MIL light, that said bank 1, Sensor 2 was bad. I checked power and ground on the plug I put my scope on the line to make sure that it was not a wiring issue. I went to the parts house and bought the only rear O2 sensor that they had. It was a bosch. Now looking at some of the forums maybe... wait for it.

Fast forward a week. I am now getting another Code. the Dread Roberts PO420.
After reading more forums I see that I needed to upgrade the Sensors in Pairs (ok lets be real I thought that was a hoax but ...)

SO I got 3 more Bosch Sensors and I replaced all four of them *this was before I read about the denso loving nature*

5 days later, I am now Getting a PO420 and PO430 Looks like I now have an efficiently issue on both banks. (I kept all the old sensors except for the B1 Rear it was bad so i tossed it)

I then decided after 15 years of working on cars/trucks that I needed to talk to someone that knows more than I do, so I went to talk to the mechanic at the dealership. He told me that Bosch makes good sensors, and he didn't think that was the problem he did agree that he didn't think that the cats were the issue and then the train took a dirt road.

So he suggested that I get a couple extra crush washers and put it on the rear sensors to get the sensor more distance from the flow..... Now... I have a feeling that he knows something I don't, but have you all heard of this sort of thing. Has that been done by anyone here?

Should I put the old rear one in Bank 2 and then get a Denso One for the Bank 1 Rear.
Should I knock the catas out and put a simulator on it....

I am really at the point where I am almost willing to try more washers. I am doing all this to avoid paying for cats ...

Please advise.

 

How is the truck running?

 

The truck is running like a top. Plenty of Power. I graphed all the PIDs from the misfire counters to airflow... spent a good hour and half sitting in the truck trying to find something that would make me think something was wrong. Since I replaced this motor and did all the work myself, I have been paranoid that something could be wrong with it. All the O2 Data from voltage to amperage look to be the same across all banks. The temp of the CATs appears to what I know is normal. around 900 to 1100 and the front to back has never been less than 50 degrees different front to back. I have to self report that most of my experience is with Fords and Dodges and not Toyota so take what i know with a twing of doesn't know historical amounts about. This is the first one i have owned. Pulled the union where both cats connect off left them hanging. Other than sounding like a Harley and getting the attention of the local sheriff... it runs close to the same with or without it going thru the cats.

 

You need a big spacer to trick the ecu. Washers aren't enough.

Something like this.

https://www.vivaperformance.com/oxygen-sensor-spacer/

P0420 is rarely sensors, it usually means they are working and the cat has failed.

Basically, the 2nd sensor is reading the same readings as the 1st sensor, there is no change or delay in gas composition.

You can usually smell it as well, a raw fuel smell from exhaust.

 

You know... I would agree except for the behavior going to bank 2 when I replaced a perfectly good sensor trying to be consistent b(based on the theory that new sensors would be *faster* from the forums). If the PO420 code would be the only code I would be cutting that cat out today. Curiosity has really got me now. Since the back sensors are so easy to get to, I think before I do something non stock, I think i am going to take Bank 2 Rear and put it it in the original Bank 1 Rear spot (I know that there was nothing wrong with that sensor). Run it for a week and see if the PO420 clears and the PO430 remains. If that is the case then I think that maybe its a Non-Oem Sensor thing.

I really do not notice the exhaust smell in the truck either way, doesn't smell rich. When I put my hand over it, the exhaust is warm/hot to the touch and feels like a good flow.... I do not have a way to test it more than that.

I want to go pull the data pids on the front and back again they were not 100% the same, but there was a consistent dataset Looking at B2 Rear vs B1 Rear... voltage and amperage on those were consistent but I did not really think to look at the differences between B1 Front and B1 Rear looking explicitly for differences.

I think in the end if the first test gives the expected results then those oxygen sensor spacers are cheaper than buying 2 more O2 senors as i am reasonably sure they are not going to let me return those. What really whomps is the 4-5 days of driving does not throw the code. So it is going to take time for me to get results from that tests.

Thanks for the prompt reply.

 

Sometimes there can be an exhaust leak within the exhaust system. where the exhaust pulse can inject air/O2 into it and tricking the sensors into false readings

 

I know you are new here (welcome!) so I thought I'd point out that @Bishop84 is actually a Toyota tech. We have a few others around too.

Have you double checked that you have no cracked manifolds or other pre cat exhaust leaks?

 

So to diagnose cats, you graph o2 sensor voltage, then change the fuel trim. (remove a vacuum line)

You watch the b1s1 and b1s2, if they both change rapidly within 1 second, its the cat. There needs to be 1-2 seconds at least for p0420 to not trigger.

B1s2 should be slow to react to changes in fuel trim.

o2 sensor voltage is a weird thing and best watched on graphs.

 

Sorry didn't mean any disrespect, I was just forming a hypothesis. Seems odd that the PO430 is new as of replacing the B2 O2 sensors for no good reason other than making them all the same. I guess it was a non intentional tone over text type of thing, I didn't meant to incite

To answer your question. I have soaked all joints with a soapy solution. When I replaced the engine, I replaced both exhaust manifold gaskets and all 4 (I call them doughnuts) but all 3 flange seals with new studs and nuts....

The soapy water trick did not show any leaks. Not sure how else to test it.

 

There's a really good diagnostic pinpoint tests that's in the FSM. Look it by the DTC number.. I can posts screens shots of the pinpoint tests later in the evening if needed.

 

Thank you so much, I was watching the graphs while my daughter drove the truck on a 12 mile loop around where i live (i live out in the middle of no where and its just a big circle)
I will do this tonight. I never thought to pull a vacuum line. That makes sense

Thank you very much.

 

IMO, the first error which complicates the diagnosing is buying Bosch sensors versus Densos.

 

I'm one of those firm believers in denso 02 sensors. Especially for Toyota/Honda. They are pretty affordable from Rock Auto. There is 5% off discount code if you find their TW thread.

 

None taken.

Was just pointing out for your confidence that he wasn't a random internet lurker tossing out something he saw on YouTube.

You also now have @Superdave1.0, another Toyota tech, who has joined in. I'm sure you'll get it worked through.

 

This is only experience. I worked at what was the world's largest midas for many years as a service advisor.
If it was a Toyota or Lexus product the Senior Master Tech ( the guy that was paid extra to fix the other guys screwups, and still fix his own jobs as well) would accept nothing but Denso brand sensors. Just that data point and nothing more.

 

If the motor was running poorly for some time, then the cats could actually be in bad shape. As a diagnostic tool, can try spark plug defoulers.

 

This is where I am stuck. I did not own the vehicle when the first engine blew up.
this is what i know. I know that there was a fist sized hole in the block on the drivers side behind the starter and the piston arm was broken in 2 places.

I do know that when I was trying to find the mysterious cause of the "mechanical" status of the auction the first thing I did was scan the codes. At that point there were no emissions related codes. and looking at distance since reset it did not look like it was just reset and then sold.

The driving reason I wanted to replace the O2 sensors (except for B1 Rear this one was bad) was the thought that if the motor blew and threw oil and radiator fluid into the exhaust that they were toast anyway.

Now that doesn't mean that there is nothing wrong with the Cat. Could very well be. I do not like performing the parts cannon approach (although reading this you are going to think that i just threw 4 O2 sensors at it) . I try and make sure I understand what exactly is broken before I throw money at parts.

This one was an attempt to logically think that those sensors were going to die if not already shot from the initial blown engine issue.

As for now the new motor runs without flaw....

 

If I had that code, the very first thing I would do is replace the downstream O2 sensor on the passenger side with a denso before thinking its a failing cat.

 

New 02 sensors I see as a maintenance item. If the vehicle has over 100k miles that is. So don't let people tell you that was a bad move. Buying bosch was a bad move though.

As stated by myself and others, start with getting DENSO 02 sensors installed. See if you can return the bosch ones you bought.

 

If it was burning coolant the cats are toast.
IF....

Bosch doesn't make bad stuff, not saying they are bad, but if Toyota could buy cheaper O2 sensors that passed their supply chain, and quality standards, they would.